☁︎Question and Answer

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?

A) m+6

• B) m+7

C) 2m+14

D) 3m+21

ANSWER EXPLANATION:

Since the average (arithmetic mean) of two numbers is equal to the sum of the two numbers divided by 2, the

equations x= m+9/2,

y=2m+15/2, z=3m+18/2

are true.

The average of x, y, and z is given by

x+y+z/3.

Substituting the expressions in m for each variable (x, y, z) gives

[m+9/2+2m+15/2+3m+18/2]/3

This fraction can be simplified to m+7.

The final answer is B.

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✍︎RainbowSparkle