The average (arithmetic mean) of 3a + 4 and another number is 2a. What is the average of the other number and a ?

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The average (arithmetic mean) of 3a + 4 and another number is 2a. What is the average of the other number and a ?

A. 2a
B. a - 4
C. a - 2
D. a + 2
E. a + 4

Answer: C
Source: Kaplan

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BTGModeratorVI wrote:
Tue Dec 15, 2020 6:58 am
The average (arithmetic mean) of 3a + 4 and another number is 2a. What is the average of the other number and a ?

A. 2a
B. a - 4
C. a - 2
D. a + 2
E. a + 4

Answer: C
Source: Kaplan
We can let n = the average of the other number and create the following equation:
(3a + 4 + n)/2 = 2a

3a + 4 + n = 4a

4 + n = a

The average of the other number and a is:

(n + 4 + n)/2 = (2n + 4)/2 = n + 2

Since n = a - 4, we can say:

n + 2 = a - 4 + 2 = a - 2

Answer: C

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