A motorist covered the first $20\, km$ of his journey in 30 mifitutes and the remaining $29\, km$ in $40\, minutes$. His average speed in $km / hr$ is:
$41 \frac{3}{4}$
$42$
$49$
$57 \frac{1}{6}$
The average monthly salary of a staff of $9$ persons is $Rs.\,2450.$ One member of the staff whose monthly salary is $Rs.\,2650$ is transferred. Find out the average salary of the remaining $8$ persons of the staff.(in $Rs.$)
The average age of $8$ men is increased by $2\,years$ when two of them whose ages are $21\, years$ and $23\, years$ are replaced by two new men. The average age of the two new men is
If the difference between the average of $x, y$ and $y$, $z$ is $12,$ then the difference between $x$ and $z$ is
Average age of $15$ students of a class is $15\, years.$ Out of these the average age of $5$ students is $14 \,years$ and that of the other $9$ students is $16\, years.$ The age of the $15^{th}$ student is (in $years$)
The average of marks obtained by $120$ candidates in a certain examination is $35 .$ If the average marks obtained by passed candidates are $39$ and those of the failed candidates are $15,$ then what is the number of candidates who passed the examination?