Find x if the mean of 2x, 4x, 2x - 13 and 6x is 4.

The mean of a set of 10 numbers is 56. If the mean of the first nine numbers is 55, find the 10th number.

The age (years) of some members in a singing group are: 12, 47, 49, 15, 43, 41, 13, 39, 43, 41 and 36.

Find the lower quartile

The age (years) of some members in a singing group are: 12, 47, 49, 15, 43, 41, 13, 39, 43, 41 and 36.

Find the mean

The mean of two numbers x and y is 4. Find the mean of four numbers x, 2x, y and 2y