The average of four numbers is 12.5. If each number is increased by 2.5, then the new average will be:

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

The average of 12 numbers is 28. If one number, 42, is replaced by another number, the average decreases by 1.5. What is the number that replaces 42?

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

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 arithmetic mean of the numbers 9, 12, 15, 18, 20, 22 is increased by 1, if 15 is replaced by