If x is the average (arithmetic mean) of m and 9, y is the average of 2m and 15, and z is the average of 3m and 18, what is the average of x, y, and z in terms of m?

Question

A) m+6

B) m+7*****

C) 2m+14

D) 3m+21

Answer 1

x = (m+9)/2
y = (2m+15)/2
z = (3m+18)/2

we want (x+y+z)/3

x+y+z = (1/2) (6m+42)
(x+y+z)/3 = (1/6)(6m+42)
= m + 7
so we agree

Answer 2

no