The average age of 4 sisters is 7 years. If we add the age of mother, then the average increases by 6 years. Find the age of the mother.

The average age of 30 boys in a class is 15 years. If we include the age of two teachers the average age increases by 1. Find the sum of ages of the two teachers.

The average of 6 numbers is 5. The first number is increased by 2, second by 4, third by 8 and so on. The average of new numbers is

Five years ago, the average age of X₁, X₂, X₃ and X₄ was 50 years. If we include X₅, the present average age of all five is 56 years. Then the present age of X₅ is

Four years ago, the average age of A and B was 20 years. If today average age of A, B and C is 25 years, what will be age of C after 7 years?

If the average of m numbers is n*n and that of n numbers is m*m , then the average of m+n numbers is