If harmonic mean of three numbers is 3 and two numbers are 2 and 6, what is third number?

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 mean of p, q, r, s and t is 280. If the mean of p, r and t is 240, what is the mean of q and s?

If M is the mean of the first 100 even natural numbers, then what is the mean of the first 100 odd natural numbers?

The sum of two numbers is 15 and their geometric mean is 20% lower than their arithmetic mean. Then the numbers will be:

The average of the first 8 numbers is 42. The average of the first 4 numbers is 40, and the average of the next 3 numbers is 44. What is the 8th number?