Find the number of ways of selecting $9$ balls from $6$ red balls, $5$ white balls and $5$ blue balls if each selection consists of $3$ balls of each colour.
There are a total of $6$ red balls, $5$ white balls, and $4$ blue balls.
$9$ balls have to be selected in such a way that each selection consists of $3$ balls of each colour. Here,
$3$ balls can be selected from $6$ red balls in $^{6} C_{3}$ ways.
$3$ balls can be selected from $5$ white balls in $^{5} C_{3}$ ways.
$3$ balls can be selected from $5$ blue balls in $^{5} C_{3}$ ways.
Thus, by multiplication principle, required number of ways of selecting $9$ balls.
$=^{6} C_{3} \times^{5} C_{3} \times^{5} C_{3}=\frac{6 !}{3 ! 3 !} \times \frac{5 !}{3 ! 2 !} \times \frac{5 !}{3 ! 2 !}$
$=\frac{6 \times 5 \times 4 \times 3 !}{3 ! \times 3 \times 2} \times \frac{5 \times 4 \times 3 !}{3 \times 2 \times 1} \times \frac{5 \times 4 \times 3 !}{3 ! \times 2 \times 1}$
$=20 \times 10 \times 10=2000$
Determine the number of $5$ card combinations out of a deck of $52$ cards if there is exactly one ace in each combination.
In an election the number of candidates is $1$ greater than the persons to be elected. If a voter can vote in $254$ ways, then the number of candidates is
Consider a class of $5$ girls and $7$ boys. The number of different teams consisting of $2$ girls and $3$ boys that can be formed from this class, if there are two specific boys $A$ and $B$, who refuse to be the members of the same team, is
Two packs of $52$ cards are shuffled together. The number of ways in which a man can be dealt $26$ cards so that he does not get two cards of the same suit and same denomination is
There are two urns. Urm $A$ has $3$ distinct red balls and urn $B$ has $9$ distinct blue balls. From each urm two balls are taken out at random and then transferred to the other. The number of ways in which this can be done is