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 $years$)
$11$
$14$
$15$
$15 \frac{2}{7}$
The average of marks obtained by $100$ candidates in a certain examination is $30 .$ If the average marks of passed candidates is $35$ and that of the failed candidates is $10,$ what is the number of candidates who passed the examination?
What is the age of a class teacher?
$I.$ There are $11$ students in the class.
$II.$ The average age of the students and the teacher is $14$ years.
$III.$ The average age of the teacher and the students is $3$ years more than that of the students.
The average marks obtained by $180$ students in an examination is $50 .$ If the average marks of passed students is $40 .$ Then what is the number of students who failed the examination ?
The average salary of all workers in a workshop is $Rs.\, 12000 .$ The average salary of $7$ technicians is $Rs.\, 15000$ and the aterage salary of the rest in $Rs.\, 9000$. The total number of workers in the workshop is:
A professional institute's total expenditure on students for a particular course is partly fixed and partly varies linearly with the number of students. The average expense per student is $Rs.\,615$ when there are $24$ students and $Rs.\,465$ when there are $40$ students. What is the average expense when there are $60$ students ? (in $Rs.$)