The average (arithmetic mean) of the five numbers in a data set is 72.

[BTGModeratorVI]

The average (arithmetic mean) of the five numbers in a data set is 72. The average (arithmetic mean) of the first three numbers is 98. What is the average (arithmetic mean) of the last two numbers?

A. 31
B. 32
C. 33
D. 34
E. 35

Answer: C
Source: Math Revolution

[Brent@GMATPrepNow]

The average (arithmetic mean) of the five numbers in a data set is 72. The average (arithmetic mean) of the first three numbers is 98. What is the average (arithmetic mean) of the last two numbers?

A. 31
B. 32
C. 33
D. 34
E. 35

Answer: C
Source: Math Revolution

Let a, b, c, d and e be the five numbers in the set.

The average (arithmetic mean) of the five numbers in a data set is 72.
So, (a + b + c + d + e)/5 = 72
Multiply both sides of the equation by 5 to get: a + b + c + d + e = 360

The average (arithmetic mean) of the first three numbers is 98.
So, (a + b + c)/3 = 98
Multiply both sides of the equation by 3 to get: a + b + c = 294

What is the average (arithmetic mean) of the last two numbers?
In other words, what is the average of d and e?

Take a + b + c + d + e = 360 and replace a + b + c with 294
We get: 294 + d + e = 360
Subtract 294 from both sides to get: d + e = 66

So, the average of d and e = (d + e)/2
= 66/2
= 33

Answer: C

[Scott@TargetTestPrep]

The average (arithmetic mean) of the five numbers in a data set is 72. The average (arithmetic mean) of the first three numbers is 98. What is the average (arithmetic mean) of the last two numbers?

A. 31
B. 32
C. 33
D. 34
E. 35

Answer: C

Solution:

Letting x = the average of the last two numbers, we can create the equation:

98(3) + 2x = 72(5)

294 + 2x = 360

2x = 66

x = 33

Answer: C