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Class 10 Mathematics · Probability · Demo

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Showing 50 of 200 questions in English

151
MediumMCQ
Match the following items:
$Q.1.$ $HCF$ of $8$ and $6$$A. 49$
$Q.2.$ $LCM$ of $(26, 91)$$B. 182$
$C. 2$
A
$Q.1-C, Q.2-B$
B
$Q.1-A, Q.2-B$
C
$Q.1-C, Q.2-A$
D
$Q.1-B, Q.2-C$

Solution

(A) Step $1$: Find the $HCF$ of $8$ and $6$.
Prime factorization of $8 = 2^3$.
Prime factorization of $6 = 2 \times 3$.
The common factor is $2$,so $HCF$ $(8, 6) = 2$.
Step $2$: Find the $LCM$ of $26$ and $91$.
Prime factorization of $26 = 2 \times 13$.
Prime factorization of $91 = 7 \times 13$.
$LCM$ $(26, 91) = 2 \times 7 \times 13 = 182$.
Therefore,$Q.1$ matches with $C$ and $Q.2$ matches with $B$.
152
MediumMCQ
Prove that $7\sqrt{5}$ is an irrational number.
A
Rational
B
Irrational
C
Integer
D
None of these

Solution

(B) Let us assume,to the contrary,that $7\sqrt{5}$ is a rational number.
Then,there exist coprime integers $a$ and $b$ $(b \neq 0)$ such that $7\sqrt{5} = \frac{a}{b}$.
Rearranging the equation,we get $\sqrt{5} = \frac{a}{7b}$.
Since $a$ and $b$ are integers,$\frac{a}{7b}$ is a rational number.
This implies that $\sqrt{5}$ is a rational number.
However,this contradicts the fact that $\sqrt{5}$ is an irrational number.
Therefore,our assumption is incorrect,and $7\sqrt{5}$ must be an irrational number.
153
DifficultMCQ
Prove that the number $\sqrt{2}$ is irrational.
A
It is a rational number.
B
It is an irrational number.
C
It is a natural number.
D
It is a whole number.

Solution

(B) Let us assume,to the contrary,that $\sqrt{2}$ is rational.
Then,there exist coprime integers $a$ and $b$ $(b \neq 0)$ such that $\sqrt{2} = \frac{a}{b}$.
Squaring both sides,we get $2 = \frac{a^2}{b^2}$,which implies $a^2 = 2b^2$.
This shows that $a^2$ is even,so $a$ must also be even.
Let $a = 2k$ for some integer $k$.
Substituting this into the equation,we get $(2k)^2 = 2b^2$,which simplifies to $4k^2 = 2b^2$,or $b^2 = 2k^2$.
This shows that $b^2$ is even,so $b$ must also be even.
Since both $a$ and $b$ are even,they have a common factor $2$,which contradicts our assumption that $a$ and $b$ are coprime.
Therefore,our assumption is false,and $\sqrt{2}$ is irrational.
154
MediumMCQ
Prove that $3 + 2\sqrt{5}$ is irrational.
A
Rational
B
Irrational
C
Integer
D
None of these

Solution

(B) Let us assume,to the contrary,that $3 + 2\sqrt{5}$ is rational.
Then,there exist coprime integers $a$ and $b$ $(b \neq 0)$ such that $3 + 2\sqrt{5} = \frac{a}{b}$.
Subtracting $3$ from both sides,we get $2\sqrt{5} = \frac{a}{b} - 3$.
$2\sqrt{5} = \frac{a - 3b}{b}$.
Dividing by $2$,we get $\sqrt{5} = \frac{a - 3b}{2b}$.
Since $a$ and $b$ are integers,$\frac{a - 3b}{2b}$ is a rational number.
This implies that $\sqrt{5}$ is a rational number.
However,this contradicts the fact that $\sqrt{5}$ is irrational.
Therefore,our assumption is incorrect,and $3 + 2\sqrt{5}$ is irrational.
155
MediumMCQ
Prove that $\sqrt{2}$ is irrational.
A
It is a rational number.
B
It is an irrational number.
C
It is an integer.
D
It is a natural number.

Solution

(B) Assume,to the contrary,that $\sqrt{2}$ is a rational number.
Then,there exist coprime integers $a$ and $b$ $(b \neq 0)$ such that $\sqrt{2} = \frac{a}{b}$.
Squaring both sides,we get $2 = \frac{a^2}{b^2}$,which implies $a^2 = 2b^2$.
This shows that $a^2$ is even,and therefore $a$ must also be even.
Let $a = 2k$ for some integer $k$.
Substituting this into the equation,we get $(2k)^2 = 2b^2$,so $4k^2 = 2b^2$,which simplifies to $b^2 = 2k^2$.
This shows that $b^2$ is even,and therefore $b$ must also be even.
Since both $a$ and $b$ are even,they have a common factor of $2$,which contradicts our assumption that $a$ and $b$ are coprime.
Thus,our assumption is false,and $\sqrt{2}$ is irrational.
156
MediumMCQ
There is a circular path around a sports field. Sonia takes $18$ minutes to drive one round of the field,while Ravi takes $12$ minutes for the same. Suppose they both start at the same point and at the same time,and go in the same direction. After how many minutes will they meet again at the starting point?
A
$36$ minutes
B
$18$ minutes
C
$6$ minutes
D
$24$ minutes

Solution

(A) To find the time when Sonia and Ravi meet again at the starting point,we need to find the Least Common Multiple $(LCM)$ of the time taken by them to complete one round.
Time taken by Sonia = $18$ minutes.
Time taken by Ravi = $12$ minutes.
Prime factorization of $18 = 2 \times 3^2$.
Prime factorization of $12 = 2^2 \times 3$.
$LCM(18, 12) = 2^2 \times 3^2 = 4 \times 9 = 36$.
Therefore,they will meet again at the starting point after $36$ minutes.
157
MediumMCQ
Explain why $7 \times 11 \times 13 + 13$ and $7 \times 6 \times 5 \times 4 \times 3 \times 2 \times 1 + 5$ are composite numbers.
A
They have only two factors.
B
They are prime numbers.
C
They have more than two factors.
D
They are odd numbers.

Solution

(C) composite number is a positive integer that has at least one divisor other than $1$ and itself.
For the first expression: $7 \times 11 \times 13 + 13 = 13 \times (7 \times 11 + 1) = 13 \times (77 + 1) = 13 \times 78 = 13 \times 13 \times 6$.
Since this number can be expressed as a product of factors other than $1$ and itself,it is a composite number.
For the second expression: $7 \times 6 \times 5 \times 4 \times 3 \times 2 \times 1 + 5 = 5 \times (7 \times 6 \times 4 \times 3 \times 2 \times 1 + 1) = 5 \times (1008 + 1) = 5 \times 1009$.
Since $1009$ is a prime number,the expression is $5 \times 1009$. This number has factors $1, 5, 1009$,and the number itself. Since it has more than two factors,it is a composite number.
158
MediumMCQ
Check whether $6^n$ can end with the digit $0$ for any natural number $n$.
A
Yes,it can end with $0$.
B
No,it cannot end with $0$.
C
It depends on the value of $n$.
D
It ends with $0$ only for even values of $n$.

Solution

(B) For any number to end with the digit $0$,its prime factorization must contain the factors $2$ and $5$.
The prime factorization of $6^n$ is $(2 \times 3)^n = 2^n \times 3^n$.
Since the prime factorization of $6^n$ only contains $2$ and $3$,it does not contain the factor $5$.
Therefore,by the Fundamental Theorem of Arithmetic,$6^n$ cannot end with the digit $0$ for any natural number $n$.
159
MediumMCQ
If $HCF(306, 657) = 9$,find $LCM(306, 657)$.
A
$22338$
B
$22383$
C
$23238$
D
$23328$

Solution

(A) We know that for any two positive integers $a$ and $b$,the relationship between their $HCF$ and $LCM$ is given by:
$HCF(a, b) \times LCM(a, b) = a \times b$
Given $a = 306$,$b = 657$,and $HCF(306, 657) = 9$.
Substituting these values into the formula:
$9 \times LCM(306, 657) = 306 \times 657$
$LCM(306, 657) = \frac{306 \times 657}{9}$
$LCM(306, 657) = 34 \times 657$
$LCM(306, 657) = 22338$
Therefore,the $LCM$ is $22338$.
160
MediumMCQ
Find the $HCF$ and $LCM$ of the integers $8$,$9$,and $25$ by the prime factorization method.
A
$HCF$ = $1$,$LCM$ = $1800$
B
$HCF$ = $3$,$LCM$ = $1800$
C
$HCF$ = $1$,$LCM$ = $900$
D
$HCF$ = $9$,$LCM$ = $1800$

Solution

(A) To find the $HCF$ and $LCM$ of $8$,$9$,and $25$ using the prime factorization method:
Step $1$: Find the prime factors of each number.
$8 = 2 \times 2 \times 2 = 2^3$
$9 = 3 \times 3 = 3^2$
$25 = 5 \times 5 = 5^2$
Step $2$: The $HCF$ is the product of the smallest power of each common prime factor. Since there are no common prime factors other than $1$,the $HCF$ is $1$.
Step $3$: The $LCM$ is the product of the greatest power of each prime factor involved in the numbers.
$LCM = 2^3 \times 3^2 \times 5^2 = 8 \times 9 \times 25 = 72 \times 25 = 1800$.
Thus,$HCF$ = $1$ and $LCM$ = $1800$.
161
MediumMCQ
Find the $HCF$ and $LCM$ of the following integers by the prime factorization method: $17, 23$ and $29$.
A
$HCF$ = $1$,$LCM$ = $11339$
B
$HCF$ = $17$,$LCM$ = $11339$
C
$HCF$ = $1$,$LCM$ = $1139$
D
$HCF$ = $23$,$LCM$ = $11339$

Solution

(A) The prime factorization of the given numbers is as follows:
$17 = 17 \times 1$
$23 = 23 \times 1$
$29 = 29 \times 1$
Since $17, 23,$ and $29$ are all prime numbers,they have no common factor other than $1$.
Therefore,the Highest Common Factor $(HCF)$ is $1$.
The Least Common Multiple $(LCM)$ is the product of the highest powers of all prime factors involved:
$LCM = 17 \times 23 \times 29 = 11339$.
Thus,$HCF$ = $1$ and $LCM$ = $11339$.
162
MediumMCQ
Find the $HCF$ and $LCM$ of the integers $12$,$15$,and $21$ by the prime factorization method.
A
$HCF = 3, LCM = 420$
B
$HCF = 3, LCM = 300$
C
$HCF = 1, LCM = 420$
D
$HCF = 1, LCM = 300$

Solution

(A) To find the $HCF$ and $LCM$ of $12$,$15$,and $21$ using prime factorization:
Step $1$: Write the prime factorization of each number.
$12 = 2^2 \times 3^1$
$15 = 3^1 \times 5^1$
$21 = 3^1 \times 7^1$
Step $2$: Find the $HCF$ (Highest Common Factor).
The $HCF$ is the product of the smallest power of each common prime factor.
The only common prime factor is $3$,and its smallest power is $3^1$.
Therefore,$HCF = 3$.
Step $3$: Find the $LCM$ (Least Common Multiple).
The $LCM$ is the product of the greatest power of each prime factor involved.
The prime factors involved are $2, 3, 5,$ and $7$.
The greatest powers are $2^2, 3^1, 5^1,$ and $7^1$.
$LCM = 2^2 \times 3^1 \times 5^1 \times 7^1 = 4 \times 3 \times 5 \times 7 = 420$.
Thus,$HCF = 3$ and $LCM = 420$.
163
DifficultMCQ
Find the $HCF$ and $LCM$ of the integers $336$ and $54$ and verify that $HCF \times LCM = \text{product of the two integers}$.
A
$HCF = 6, LCM = 3024; 18144 = 18144$
B
$HCF = 12, LCM = 1512; 18144 = 18144$
C
$HCF = 6, LCM = 3024; 18144 = 18144$
D
$HCF = 18, LCM = 1008; 18144 = 18144$

Solution

(A) Step $1$: Prime factorization of $336$ and $54$.
$336 = 2^4 \times 3^1 \times 7^1$
$54 = 2^1 \times 3^3$
Step $2$: Find $HCF$.
$HCF = 2^{\min(4,1)} \times 3^{\min(1,3)} = 2^1 \times 3^1 = 6$.
Step $3$: Find $LCM$.
$LCM = 2^{\max(4,1)} \times 3^{\max(1,3)} \times 7^1 = 2^4 \times 3^3 \times 7 = 16 \times 27 \times 7 = 3024$.
Step $4$: Verify $HCF \times LCM = \text{Product of integers}$.
$HCF \times LCM = 6 \times 3024 = 18144$.
$\text{Product of integers} = 336 \times 54 = 18144$.
Since $18144 = 18144$, the relationship is verified.
164
DifficultMCQ
Find the $HCF$ and $LCM$ of the following pair of integers $510$ and $92$ and verify that $HCF \times LCM = \text{product of the two numbers}$.
A
$HCF = 2, LCM = 23460$
B
$HCF = 4, LCM = 23460$
C
$HCF = 2, LCM = 23640$
D
$HCF = 4, LCM = 23640$

Solution

(A) Step $1$: Find the prime factorization of $510$ and $92$.
$510 = 2 \times 3 \times 5 \times 17$
$92 = 2^2 \times 23$
Step $2$: Find $HCF$ and $LCM$.
$HCF = 2^1 = 2$
$LCM = 2^2 \times 3 \times 5 \times 17 \times 23 = 23460$
Step $3$: Verify the relationship $HCF \times LCM = \text{product of the two numbers}$.
$HCF \times LCM = 2 \times 23460 = 46920$
$\text{Product of numbers} = 510 \times 92 = 46920$
Since $46920 = 46920$,the relationship is verified.
165
MediumMCQ
Find the $HCF$ and $LCM$ of the following pairs of integers and verify that $HCF \times LCM = \text{product of the two numbers}: 26$ and $91$.
A
$HCF = 13, LCM = 182; 2366 = 2366$
B
$HCF = 13, LCM = 182; 2366 \neq 2366$
C
$HCF = 26, LCM = 91; 2366 = 2366$
D
$HCF = 1, LCM = 2366; 2366 = 2366$

Solution

(A) Step $1$: Prime factorization of $26$ and $91$.
$26 = 2 \times 13$
$91 = 7 \times 13$
Step $2$: Find $HCF$ and $LCM$.
$HCF = \text{Product of the smallest power of each common prime factor} = 13$.
$LCM = \text{Product of the greatest power of each prime factor involved} = 2 \times 7 \times 13 = 182$.
Step $3$: Verify the relationship $HCF \times LCM = \text{Product of the two numbers}$.
$HCF \times LCM = 13 \times 182 = 2366$.
$\text{Product of the two numbers} = 26 \times 91 = 2366$.
Since $2366 = 2366$, the relationship is verified.
166
MediumMCQ
Express the number $7429$ as a product of its prime factors.
A
$17 \times 19 \times 23$
B
$13 \times 17 \times 23$
C
$17 \times 19 \times 29$
D
$11 \times 19 \times 23$

Solution

(A) To find the prime factors of $7429$,we test divisibility by prime numbers sequentially.
$7429$ is not divisible by $2, 3, 5, 7, 11,$ or $13$.
Testing $17$: $7429 \div 17 = 437$.
Now,we find the prime factors of $437$.
Testing $19$: $437 \div 19 = 23$.
Since $23$ is a prime number,the prime factorization is $17 \times 19 \times 23$.
167
EasyMCQ
Express the number $5005$ as a product of its prime factors.
A
$5 \times 7 \times 11 \times 13$
B
$5 \times 7 \times 11 \times 17$
C
$5 \times 7 \times 13 \times 17$
D
$5 \times 11 \times 13 \times 17$

Solution

(A) To find the prime factors of $5005$,we perform successive division by prime numbers:
$1$. Since the last digit is $5$,it is divisible by $5$: $5005 \div 5 = 1001$.
$2$. Now,divide $1001$ by the next prime number,$7$: $1001 \div 7 = 143$.
$3$. Next,divide $143$ by the next prime number,$11$: $143 \div 11 = 13$.
$4$. Finally,$13$ is a prime number,so $13 \div 13 = 1$.
Therefore,the prime factorization of $5005$ is $5 \times 7 \times 11 \times 13$.
168
MediumMCQ
Express the number $3825$ as a product of its prime factors.
A
$3 \times 5^2 \times 17$
B
$3^2 \times 5^2 \times 17$
C
$3^2 \times 5^3 \times 17$
D
$3 \times 5^3 \times 17$

Solution

(B) To find the prime factors of $3825$,we perform successive division by prime numbers:
$1$. Since the last digit is $5$,it is divisible by $5$: $3825 \div 5 = 765$.
$2$. $765$ is also divisible by $5$: $765 \div 5 = 153$.
$3$. Now,check for $3$: The sum of digits of $153$ is $1+5+3 = 9$,which is divisible by $3$. So,$153 \div 3 = 51$.
$4$. $51$ is divisible by $3$: $51 \div 3 = 17$.
$5$. $17$ is a prime number,so $17 \div 17 = 1$.
Thus,the prime factorization is $3825 = 3 \times 3 \times 5 \times 5 \times 17 = 3^2 \times 5^2 \times 17$.
169
EasyMCQ
Express the number $156$ as a product of its prime factors.
A
$2^2 \times 3 \times 13$
B
$2 \times 3^2 \times 13$
C
$2^2 \times 3^2 \times 13$
D
$2 \times 3 \times 13^2$

Solution

(A) To express $156$ as a product of its prime factors,we perform prime factorization:
$156 = 2 \times 78$
$78 = 2 \times 39$
$39 = 3 \times 13$
Combining these,we get $156 = 2 \times 2 \times 3 \times 13$.
In exponential form,this is $2^2 \times 3 \times 13$.
170
EasyMCQ
Express the number $140$ as a product of its prime factors.
A
$2 \times 2 \times 5 \times 7$
B
$2^2 \times 5 \times 7$
C
$2 \times 5^2 \times 7$
D
$2 \times 5 \times 7^2$

Solution

(B) To express $140$ as a product of its prime factors,we perform prime factorization:
$1$. Divide $140$ by the smallest prime number,$2$: $140 \div 2 = 70$.
$2$. Divide $70$ by $2$: $70 \div 2 = 35$.
$3$. Divide $35$ by the next smallest prime number,$5$: $35 \div 5 = 7$.
$4$. Divide $7$ by the prime number $7$: $7 \div 7 = 1$.
Thus,$140 = 2 \times 2 \times 5 \times 7$.
In exponential form,this is $2^2 \times 5 \times 7$.
171
MediumMCQ
Use Euclid's division algorithm to find the $HCF$ of $867$ and $255$.
A
$51$
B
$102$
C
$17$
D
$255$

Solution

(A) To find the $HCF$ of $867$ and $255$ using Euclid's division algorithm,we follow these steps:
Step $1$: Since $867 > 255$,we apply Euclid's division lemma to $867$ and $255$:
$867 = 255 \times 3 + 102$
Step $2$: Since the remainder $102 \neq 0$,we apply the lemma to $255$ and $102$:
$255 = 102 \times 2 + 51$
Step $3$: Since the remainder $51 \neq 0$,we apply the lemma to $102$ and $51$:
$102 = 51 \times 2 + 0$
Since the remainder is now $0$,the divisor at this stage is the $HCF$.
Therefore,the $HCF$ of $867$ and $255$ is $51$.
172
MediumMCQ
Use Euclid's division algorithm to find the $HCF$ of $135$ and $225$.
A
$45$
B
$35$
C
$15$
D
$25$

Solution

(A) To find the $HCF$ of $135$ and $225$ using Euclid's division algorithm,we follow these steps:
Step $1$: Since $225 > 135$,we apply Euclid's division lemma to $225$ and $135$:
$225 = 135 \times 1 + 90$
Step $2$: Since the remainder $90 \neq 0$,we apply the lemma to $135$ and $90$:
$135 = 90 \times 1 + 45$
Step $3$: Since the remainder $45 \neq 0$,we apply the lemma to $90$ and $45$:
$90 = 45 \times 2 + 0$
Since the remainder is $0$,the divisor at this stage is the $HCF$.
Therefore,the $HCF$ of $135$ and $225$ is $45$.
173
MediumMCQ
Without performing long division,state whether the decimal expansion of the rational number $\frac{13}{3125}$ is terminating or non-terminating repeating.
A
Terminating
B
Non-terminating repeating
C
Non-terminating non-repeating
D
None of these

Solution

(A) To determine if the decimal expansion of a rational number $\frac{p}{q}$ is terminating,we examine the prime factorization of the denominator $q$.
If $q$ is of the form $2^n \times 5^m$,where $n$ and $m$ are non-negative integers,then the decimal expansion is terminating.
Given the rational number $\frac{13}{3125}$,the denominator is $q = 3125$.
Prime factorization of $3125 = 5 \times 5 \times 5 \times 5 \times 5 = 5^5$.
This can be written as $2^0 \times 5^5$.
Since the denominator is in the form $2^n \times 5^m$ (where $n=0$ and $m=5$),the decimal expansion of $\frac{13}{3125}$ is terminating.
174
Medium
Prove that $\sqrt{2}$ is irrational.

Solution

(N/A) Let us assume,to the contrary,that $\sqrt{2}$ is rational.
Then,there exist coprime integers $a$ and $b$ $(b \neq 0)$ such that $\sqrt{2} = \frac{a}{b}$.
Squaring both sides,we get $2 = \frac{a^2}{b^2}$,which implies $a^2 = 2b^2$.
This shows that $a^2$ is divisible by $2$,and consequently,$a$ is also divisible by $2$ (by the Fundamental Theorem of Arithmetic).
So,we can write $a = 2k$ for some integer $k$.
Substituting this into the equation $a^2 = 2b^2$,we get $(2k)^2 = 2b^2$,which simplifies to $4k^2 = 2b^2$,or $b^2 = 2k^2$.
This shows that $b^2$ is divisible by $2$,and consequently,$b$ is also divisible by $2$.
Thus,both $a$ and $b$ have at least $2$ as a common factor,which contradicts our assumption that $a$ and $b$ are coprime.
Therefore,our assumption that $\sqrt{2}$ is rational is false,and $\sqrt{2}$ must be irrational.
175
Medium
Prove that $\sqrt{2}$ is irrational.

Solution

(A) Let us assume,to the contrary,that $\sqrt{2}$ is rational.
Then,there exist coprime integers $a$ and $b$ $(b \neq 0)$ such that $\sqrt{2} = \frac{a}{b}$.
Squaring both sides,we get $2 = \frac{a^2}{b^2}$,which implies $a^2 = 2b^2$.
This means $a^2$ is divisible by $2$,and consequently,$a$ is also divisible by $2$ (by the Fundamental Theorem of Arithmetic).
So,we can write $a = 2k$ for some integer $k$.
Substituting this into $a^2 = 2b^2$,we get $(2k)^2 = 2b^2$,which simplifies to $4k^2 = 2b^2$,or $b^2 = 2k^2$.
This implies $b^2$ is divisible by $2$,and consequently,$b$ is also divisible by $2$.
Thus,both $a$ and $b$ have at least $2$ as a common factor,which contradicts our assumption that $a$ and $b$ are coprime.
Therefore,our assumption is false,and $\sqrt{2}$ is irrational.
176
Medium
Prove that $3\sqrt{2}$ is an irrational number.

Solution

(N/A) Let us assume,to the contrary,that $3\sqrt{2}$ is a rational number.
Then,there exist coprime integers $a$ and $b$ $(b \neq 0)$ such that $3\sqrt{2} = \frac{a}{b}$.
This can be rearranged as $\sqrt{2} = \frac{a}{3b}$.
Since $a$ and $b$ are integers,$\frac{a}{3b}$ is a rational number.
This implies that $\sqrt{2}$ is a rational number.
However,this contradicts the fact that $\sqrt{2}$ is an irrational number.
Therefore,our assumption that $3\sqrt{2}$ is a rational number is incorrect.
Hence,$3\sqrt{2}$ is an irrational number.
177
MediumMCQ
Prove that $5 - \sqrt{3}$ is an irrational number.
A
Rational
B
Irrational
C
Integer
D
None of these

Solution

(B) Let us assume,to the contrary,that $5 - \sqrt{3}$ is a rational number.
Then,there exist coprime integers $a$ and $b$ $(b \neq 0)$ such that $5 - \sqrt{3} = \frac{a}{b}$.
Rearranging the equation,we get $5 - \frac{a}{b} = \sqrt{3}$,which simplifies to $\frac{5b - a}{b} = \sqrt{3}$.
Since $a$ and $b$ are integers,$\frac{5b - a}{b}$ is a rational number.
This implies that $\sqrt{3}$ is a rational number.
However,this contradicts the fact that $\sqrt{3}$ is an irrational number.
Therefore,our assumption is incorrect,and $5 - \sqrt{3}$ must be an irrational number.
178
Medium
Prove that $\sqrt{2}$ is an irrational number.

Solution

(N/A) Let us assume,to the contrary,that $\sqrt{2}$ is a rational number.
Then,there exist coprime integers $a$ and $b$ $(b \neq 0)$ such that $\sqrt{2} = \frac{a}{b}$.
Squaring both sides,we get $2 = \frac{a^2}{b^2}$,which implies $a^2 = 2b^2$.
This means $a^2$ is divisible by $2$,so $a$ must also be divisible by $2$ (by the Fundamental Theorem of Arithmetic).
Let $a = 2k$ for some integer $k$.
Substituting this into $a^2 = 2b^2$,we get $(2k)^2 = 2b^2$,which simplifies to $4k^2 = 2b^2$,or $b^2 = 2k^2$.
This means $b^2$ is divisible by $2$,so $b$ must also be divisible by $2$.
Since both $a$ and $b$ are divisible by $2$,they have a common factor of $2$,which contradicts our assumption that $a$ and $b$ are coprime.
Therefore,our assumption is false,and $\sqrt{2}$ is an irrational number.
179
MediumMCQ
Find the $HCF$ and $LCM$ of $6$,$72$,and $120$ using the prime factorization method.
A
$HCF$ = $6$,$LCM$ = $360$
B
$HCF$ = $12$,$LCM$ = $360$
C
$HCF$ = $6$,$LCM$ = $720$
D
$HCF$ = $12$,$LCM$ = $720$

Solution

(A) To find the $HCF$ and $LCM$ of $6$,$72$,and $120$ using prime factorization:
Step $1$: Find the prime factors of each number.
$6 = 2^1 \times 3^1$
$72 = 2^3 \times 3^2$
$120 = 2^3 \times 3^1 \times 5^1$
Step $2$: The $HCF$ is the product of the smallest power of each common prime factor.
$HCF = 2^1 \times 3^1 = 6$
Step $3$: The $LCM$ is the product of the greatest power of each prime factor involved.
$LCM = 2^3 \times 3^2 \times 5^1 = 8 \times 9 \times 5 = 360$
Thus,the $HCF$ is $6$ and the $LCM$ is $360$.
180
MediumMCQ
Find the $HCF$ of $96$ and $404$ by the prime factorization method,and hence find their $LCM$.
A
$HCF = 4, LCM = 9696$
B
$HCF = 4, LCM = 9690$
C
$HCF = 2, LCM = 9696$
D
$HCF = 4, LCM = 9796$

Solution

(A) Step $1$: Find the prime factorization of $96$ and $404$.
$96 = 2^5 \times 3^1$
$404 = 2^2 \times 101^1$
Step $2$: Find the $HCF$ by taking the smallest power of each common prime factor.
$HCF(96, 404) = 2^2 = 4$.
Step $3$: Use the relationship $LCM(a, b) \times HCF(a, b) = a \times b$.
$LCM(96, 404) = \frac{96 \times 404}{HCF(96, 404)}$
$LCM(96, 404) = \frac{96 \times 404}{4} = 96 \times 101 = 9696$.
181
MediumMCQ
Find the $HCF$ and $LCM$ of $6$ and $20$ using the prime factorization method.
A
$HCF$ = $2$,$LCM$ = $60$
B
$HCF$ = $2$,$LCM$ = $120$
C
$HCF$ = $4$,$LCM$ = $60$
D
$HCF$ = $6$,$LCM$ = $20$

Solution

(A) Step $1$: Find the prime factorization of the given numbers.
$6 = 2 \times 3$
$20 = 2^2 \times 5$
Step $2$: To find the $HCF$,take the product of the smallest power of each common prime factor.
Common prime factor is $2$. The smallest power is $2^1$.
Therefore,$HCF$ = $2$.
Step $3$: To find the $LCM$,take the product of the highest power of each prime factor involved.
Prime factors involved are $2, 3,$ and $5$.
Highest powers are $2^2, 3^1,$ and $5^1$.
$LCM$ = $2^2 \times 3^1 \times 5^1 = 4 \times 3 \times 5 = 60$.
Thus,$HCF$ = $2$ and $LCM$ = $60$.
182
MediumMCQ
Check whether $4^n$ can end with the digit $0$ for any positive integer $n$.
A
Yes,it can end with $0$.
B
No,it cannot end with $0$.
C
It depends on the value of $n$.
D
It ends with $0$ only if $n$ is even.

Solution

(B) For a number to end with the digit $0$,it must be divisible by $10$.
This means its prime factorization must contain both $2$ and $5$ as factors.
The prime factorization of $4^n$ is $(2^2)^n = 2^{2n}$.
Since the only prime factor of $4^n$ is $2$,it does not contain $5$ as a factor.
Therefore,$4^n$ can never end with the digit $0$ for any positive integer $n$.
183
MediumMCQ
Find the remainder when $p(x) = 40x^2 + 11x - 63$ is divided by $x + 2$.
A
$245$
B
$75$
C
$85$
D
-$75$

Solution

(B) According to the Remainder Theorem,if a polynomial $p(x)$ is divided by $(x - a)$,the remainder is $p(a)$.
Here,the divisor is $x + 2$,which can be written as $x - (-2)$.
Therefore,$a = -2$.
Now,substitute $x = -2$ into the polynomial $p(x) = 40x^2 + 11x - 63$:
$p(-2) = 40(-2)^2 + 11(-2) - 63$
$p(-2) = 40(4) - 22 - 63$
$p(-2) = 160 - 22 - 63$
$p(-2) = 160 - 85$
$p(-2) = 75$
Thus,the remainder is $75$.
184
MediumMCQ
If $p(x) = 2x^4 - 3x^3 + 7x + 5$,then the value of $p(-2)$ is:
A
$0$
B
-$1$
C
$27$
D
$47$

Solution

(D) To find the value of $p(-2)$,substitute $x = -2$ into the given polynomial $p(x) = 2x^4 - 3x^3 + 7x + 5$.
$p(-2) = 2(-2)^4 - 3(-2)^3 + 7(-2) + 5$
Calculate the powers:
$(-2)^4 = 16$
$(-2)^3 = -8$
Substitute these values back into the expression:
$p(-2) = 2(16) - 3(-8) + 7(-2) + 5$
$p(-2) = 32 + 24 - 14 + 5$
$p(-2) = 56 - 14 + 5$
$p(-2) = 42 + 5$
$p(-2) = 47$
185
EasyMCQ
If $P(-7) = 0$,then one factor of $P(x)$ is . . . . . . .
A
$x - 7$
B
$x + 1$
C
$x + 7$
D
$x - 1$

Solution

(C) According to the Factor Theorem,if $P(a) = 0$ for a polynomial $P(x)$,then $(x - a)$ is a factor of $P(x)$.
Given that $P(-7) = 0$,we substitute $a = -7$ into the theorem.
Therefore,$(x - (-7))$ is a factor of $P(x)$.
This simplifies to $(x + 7)$ being a factor of $P(x)$.
186
MediumMCQ
If two zeros of the polynomial $p(x) = x^3 + x^2 - 5x - 5$ are $\sqrt{5}$ and $-\sqrt{5}$,then the third zero is . . . . . . .
A
$1$
B
-$1$
C
$2$
D
-$2$

Solution

(B) Let the zeros of the cubic polynomial $p(x) = ax^3 + bx^2 + cx + d$ be $\alpha, \beta,$ and $\gamma$.
Given: $\alpha = \sqrt{5}$,$\beta = -\sqrt{5}$,and we need to find $\gamma$.
According to the relationship between zeros and coefficients of a cubic polynomial,the sum of the zeros is given by:
$\alpha + \beta + \gamma = -\frac{b}{a}$
From the polynomial $p(x) = x^3 + x^2 - 5x - 5$,we have $a = 1$ and $b = 1$.
Substituting the values:
$\sqrt{5} + (-\sqrt{5}) + \gamma = -\frac{1}{1}$
$0 + \gamma = -1$
$\gamma = -1$
Thus,the third zero is $-1$.
187
EasyMCQ
The graph of the linear polynomial $p(x) = 5x + 3$ is a . . . . . . .
A
straight line
B
parabola
C
ray
D
line segment

Solution

(A) linear polynomial is of the form $p(x) = ax + b$,where $a \neq 0$. The graph of a linear polynomial always represents a straight line in the Cartesian plane. Since $p(x) = 5x + 3$ is a linear polynomial,its graph is a straight line.
188
MediumMCQ
For the zeros $\alpha$ and $\beta$ of the polynomial $p(x) = ax^2 + bx + c$,what is the value of $\frac{1}{\alpha} + \frac{1}{\beta}$?
A
$-\frac{b}{c}$
B
$-\frac{b}{a}$
C
$\frac{c}{a}$
D
None of these

Solution

(A) Given the polynomial $p(x) = ax^2 + bx + c$ with zeros $\alpha$ and $\beta$.
From the relationship between zeros and coefficients:
Sum of zeros: $\alpha + \beta = -\frac{b}{a}$
Product of zeros: $\alpha \cdot \beta = \frac{c}{a}$
We need to find $\frac{1}{\alpha} + \frac{1}{\beta}$.
Taking the common denominator: $\frac{1}{\alpha} + \frac{1}{\beta} = \frac{\alpha + \beta}{\alpha \cdot \beta}$.
Substituting the values: $\frac{-\frac{b}{a}}{\frac{c}{a}} = -\frac{b}{a} \cdot \frac{a}{c} = -\frac{b}{c}$.
Therefore,the correct option is $A$.
189
MediumMCQ
The factors of the quadratic polynomial $p(x) = x^2 + 4x - 5$ are . . . . . . .
A
$(x - 1)(x - 5)$
B
$(x + 5)(x + 1)$
C
$(x + 5)(x - 1)$
D
$(x + 1)(x - 5)$

Solution

(C) To factorize the quadratic polynomial $p(x) = x^2 + 4x - 5$,we need to find two numbers whose product is $-5$ and whose sum is $4$.
These two numbers are $5$ and $-1$,because $5 \times (-1) = -5$ and $5 + (-1) = 4$.
Now,rewrite the middle term $4x$ as $5x - x$:
$p(x) = x^2 + 5x - x - 5$
Group the terms:
$p(x) = (x^2 + 5x) - (x + 5)$
Factor out the common terms:
$p(x) = x(x + 5) - 1(x + 5)$
Finally,factor out $(x + 5)$:
$p(x) = (x + 5)(x - 1)$.
190
MediumMCQ
For the polynomial $p(x) = x^2 - 4x + 3$,the value of $\alpha + \beta$ is . . . . . . .
A
Zero
B
Negative integer
C
Positive fraction
D
Positive integer

Solution

(D) For a quadratic polynomial of the form $ax^2 + bx + c$,the sum of the zeros $\alpha + \beta$ is given by the formula $\alpha + \beta = -b/a$.
Comparing $p(x) = x^2 - 4x + 3$ with $ax^2 + bx + c$,we get $a = 1$,$b = -4$,and $c = 3$.
Substituting these values into the formula: $\alpha + \beta = -(-4)/1 = 4/1 = 4$.
Since $4$ is a positive integer,the correct option is $D$.
191
MediumMCQ
The graph of the polynomial $p(x) = ax - b$,where $a \neq 0$ and $a, b \in R$,intersects the $X$-axis at which unique point?
A
$(-\frac{b}{a}, 0)$
B
$(0, \frac{b}{a})$
C
$(\frac{b}{a}, 0)$
D
$(\frac{a}{b}, 0)$

Solution

(C) To find the point where the graph of the polynomial $p(x) = ax - b$ intersects the $X$-axis,we set $p(x) = 0$.
Setting $ax - b = 0$ gives $ax = b$.
Solving for $x$,we get $x = \frac{b}{a}$.
Since the point lies on the $X$-axis,its y-coordinate is $0$.
Therefore,the graph intersects the $X$-axis at the point $(\frac{b}{a}, 0)$.
192
MediumMCQ
The number of real zeros of the polynomial $p(x) = x^3 - x$ is . . . . . . .
A
$3$
B
$1$
C
$2$
D
$0$

Solution

(A) To find the zeros of the polynomial $p(x) = x^3 - x$,we set $p(x) = 0$.
$x^3 - x = 0$
Factor out $x$:
$x(x^2 - 1) = 0$
Using the difference of squares formula $a^2 - b^2 = (a - b)(a + b)$:
$x(x - 1)(x + 1) = 0$
Setting each factor to zero,we get:
$x = 0$,$x - 1 = 0 \implies x = 1$,and $x + 1 = 0 \implies x = -1$.
Thus,the zeros are $0, 1, -1$.
There are $3$ real zeros.
193
MediumMCQ
The degree of the polynomial $(x+1)(x^2 - x - x^4 + 1)$ is . . . . . . .
A
$3$
B
$4$
C
$5$
D
$1$

Solution

(C) To find the degree of the polynomial $(x+1)(x^2 - x - x^4 + 1)$,we identify the highest power of $x$ in each factor.
The first factor is $(x+1)$,which has a degree of $1$.
The second factor is $(x^2 - x - x^4 + 1)$,which has a degree of $4$ (since the highest power of $x$ is $x^4$).
When multiplying two polynomials,the degree of the resulting polynomial is the sum of the degrees of the individual factors.
Therefore,the degree of the product is $1 + 4 = 5$.
194
MediumMCQ
If $\alpha$ and $\beta$ are the zeros of the polynomial $P(x) = x^2 - 3x + 2k$ and $\alpha + \beta = \alpha\beta$,then the value of $k$ is:
A
$3/2$
B
$-3$
C
$3$
D
$1$

Solution

(A) For a quadratic polynomial $ax^2 + bx + c$,the sum of zeros $\alpha + \beta = -b/a$ and the product of zeros $\alpha\beta = c/a$.
Given the polynomial $P(x) = x^2 - 3x + 2k$,we have $a = 1$,$b = -3$,and $c = 2k$.
Thus,$\alpha + \beta = -(-3)/1 = 3$ and $\alpha\beta = 2k/1 = 2k$.
According to the problem,$\alpha + \beta = \alpha\beta$.
Substituting the values,we get $3 = 2k$.
Therefore,$k = 3/2$.
195
MediumMCQ
The zero of the polynomial $p(x) = \sqrt{5}x - 5$ is . . . . . . .
A
$-\sqrt{5}$
B
$\sqrt{5}$
C
$\frac{\sqrt{5}}{5}$
D
$-5$

Solution

(B) To find the zero of the polynomial $p(x) = \sqrt{5}x - 5$,we set $p(x) = 0$.
So,$\sqrt{5}x - 5 = 0$.
Adding $5$ to both sides,we get $\sqrt{5}x = 5$.
Dividing both sides by $\sqrt{5}$,we get $x = \frac{5}{\sqrt{5}}$.
Rationalizing the denominator,$x = \frac{5 \cdot \sqrt{5}}{\sqrt{5} \cdot \sqrt{5}} = \frac{5\sqrt{5}}{5} = \sqrt{5}$.
Therefore,the zero of the polynomial is $\sqrt{5}$.
196
EasyMCQ
The product of the zeros of the polynomial $x^{2}-4x+3$ is . . . . . . .
A
$1$
B
$4$
C
-$4$
D
$3$

Solution

(D) For a quadratic polynomial of the form $ax^{2}+bx+c$,the product of the zeros is given by the formula $\frac{c}{a}$.
Comparing the given polynomial $x^{2}-4x+3$ with the standard form $ax^{2}+bx+c$,we have $a=1$,$b=-4$,and $c=3$.
Therefore,the product of the zeros = $\frac{c}{a} = \frac{3}{1} = 3$.
Thus,the correct option is $D$.
197
EasyMCQ
If $\alpha, \beta$,and $\gamma$ are the zeros of the cubic polynomial $p(x) = ax^3 + bx^2 + cx + d$ where $a \neq 0$,then the product of its zeros $(\alpha \beta \gamma)$ is:
A
$-\frac{d}{a}$
B
$\frac{c}{a}$
C
$-\frac{b}{a}$
D
$\frac{a}{b}$

Solution

(A) For a cubic polynomial $p(x) = ax^3 + bx^2 + cx + d$,the relationship between the coefficients and the zeros $(\alpha, \beta, \gamma)$ are given by:
$1$. Sum of zeros: $\alpha + \beta + \gamma = -\frac{b}{a}$
$2$. Sum of product of zeros taken two at a time: $\alpha\beta + \beta\gamma + \gamma\alpha = \frac{c}{a}$
$3$. Product of zeros: $\alpha\beta\gamma = -\frac{d}{a}$
Therefore,the product of the zeros is $-\frac{d}{a}$.
198
MediumMCQ
If $\frac{x^{3}-1}{p(x)}=\frac{x^{2}+x+1}{x-1}$,then $p(x) = \dots$
A
$(x-1)^{2}$
B
$x^{2}-1$
C
$x+1$
D
$1$

Solution

(A) Given the equation: $\frac{x^{3}-1}{p(x)} = \frac{x^{2}+x+1}{x-1}$.
We know the algebraic identity for the difference of cubes: $x^{3}-1 = (x-1)(x^{2}+x+1)$.
Substituting this into the equation: $\frac{(x-1)(x^{2}+x+1)}{p(x)} = \frac{x^{2}+x+1}{x-1}$.
By canceling $(x^{2}+x+1)$ from both sides (assuming $x^{2}+x+1 \neq 0$): $\frac{x-1}{p(x)} = \frac{1}{x-1}$.
Cross-multiplying gives: $p(x) = (x-1)(x-1) = (x-1)^{2}$.
199
MediumMCQ
Which of the following is not a polynomial in variable $x$?
A
$4x^2 + \sqrt{7}$
B
$3x^2 + x - 1$
C
$3x^2 - 5\sqrt{x} + 2$
D
$3x - 1$

Solution

(C) polynomial is an algebraic expression where the exponents of the variable must be non-negative integers.
In option $A$,$4x^2 + \sqrt{7}$,the exponent of $x$ is $2$,which is a non-negative integer.
In option $B$,$3x^2 + x - 1$,the exponents of $x$ are $2$ and $1$,which are non-negative integers.
In option $C$,$3x^2 - 5\sqrt{x} + 2$,the term $\sqrt{x}$ can be written as $x^{1/2}$. Since $1/2$ is not an integer,this expression is not a polynomial.
In option $D$,$3x - 1$,the exponent of $x$ is $1$,which is a non-negative integer.
Therefore,$3x^2 - 5\sqrt{x} + 2$ is not a polynomial.
200
MediumMCQ
If $x+4$ is a factor of the polynomial $x^{2}+7x+m$,then $m = $ . . . . . .
A
$3$
B
$12$
C
$4$
D
$7$

Solution

(B) Let the polynomial be $p(x) = x^{2} + 7x + m$.
Since $(x+4)$ is a factor of $p(x)$,by the Factor Theorem,$p(-4) = 0$.
Substituting $x = -4$ into the polynomial:
$(-4)^{2} + 7(-4) + m = 0$
$16 - 28 + m = 0$
$-12 + m = 0$
$m = 12$.
Therefore,the value of $m$ is $12$.

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