The arithmic mean of a set of 7 numbers is 20. The arithmic mean of a second set of 13 numbers is 40. What is the mean of all 20 numbers? 31, 32, 33, 34 or not enough information

Answer 1

Since 'mean' is just another say of saying 'average', represent the sum of values of the first set as x and the second set as y. Then

x/7 = 20 -> x = 140

y/13 = 40 -> y = 520

The mean of all the numbers together would be the sum of all the numbers divided by how many there are, so

(x+y)/(7+13) = (140+520)/20 = 660/20 = 33