The average age of students of a class is $15.8 \,years.$ The average age of boys in the class is $16.4$ $years$ and that of the girls is $15.4\, years.$ The ratio of number of boys to the number of girls in the class is:
$1: 2$
$3: 4$
$3: 5$
$2: 3$
The average of five consecutive odd integers is $27 .$ What is the product of the first and the last number?
Find average of all prime numbers between $60$ and $90.$
The average of $6$ numbers is $20 .$ If one number is removed, the average becomes $15 .$ What is the number removed?
The average weight of $8$ persons increases by $2.5\, kg$ when a new person comes in place of one of them weighing $65\, kg$. What might be the weight of the new person? (in $kg$)
The average of three consecutive odd numbers is $52$ more than $\frac{1}{3}$$^{rd}$ of the largest of these numbers. What is the smallest of these numbers ?