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The average (arithmetic mean) of 10, 30, and 50 is 5 more than the average of 20, 40, and

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Re: The average (arithmetic mean) of 10, 30, and 50 is 5 more than the average of 20, 40, and

by Brent@GMATPrepNow » Fri Jan 01, 2021 6:57 am
BTGModeratorVI wrote: ↑
Wed Dec 16, 2020 12:38 pm
 The average (arithmetic mean) of 10, 30, and 50 is 5 more than the average of 20, 40, and

(A) 15
(B) 25
(C) 35
(D) 45
(E) 55

Answer: A
Source: official guide
Let x = the missing (required number)
Average of 10, 30, and 50 = (10 + 30 + 50)/3 = 90/3 = 30
Average of 20, 40, and x = (20 + 40 + x)/3 = (60 + x)/3

The average (arithmetic mean) of 10, 30, and 50 is 5 more than the average of 20, 40, and
So, 30 = (60 + x)/3 + 5
Subtract 5 from both sides to get: 25 = (60 + x)/3
Multiply both sides by 3 to get: 75 = 60 + x
Solve: x = 15

Answer: A

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Brent
Brent Hanneson - Creator of GMATPrepNow.com
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