The average of a set of 5 numbers is 20. If 4 additional numbers are added to the set, the average...

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by AAPL » Tue Jun 30, 2020 12:56 am

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The average of a set of 5 numbers is 20. If 4 additional numbers are added to the set, the average increases to 24. What is the average of the additional 4 numbers?

A. 22
B. 25
C. 26
D. 28
E. 29

OA E

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Source: Beat The GMAT — Problem Solving | Tue Jun 30, 2020 12:56 am

ssrivastava: Junior | Next Rank: 30 Posts; Posts: 17; Joined: Sat Nov 30, 2019 10:06 pm

Re: The average of a set of 5 numbers is 20. If 4 additional numbers are added to the set, the average...

by ssrivastava » Tue Jun 30, 2020 2:39 am

Let N be the Total of 5 Nos. Thus, the average will be N/5=20. So, N=100
let x'be the sum of 4 additional numbers. The new avg = (n+x')/5+4=24. So, N+X'= 216

From the above, X'=116. This X' is the sum of 4 new numbers. The avg = 116/4=29

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Scott@TargetTestPrep: GMAT Instructor; Posts: 8208; Joined: Sat Apr 25, 2015 10:56 amFollowed by: 29 members; Location: Los Angeles, CA; Thanked: 43 times

Re: The average of a set of 5 numbers is 20. If 4 additional numbers are added to the set, the average...

by Scott@TargetTestPrep » Mon Apr 19, 2021 6:16 am

AAPL wrote: ↑
Tue Jun 30, 2020 12:56 am
Veritas Prep

The average of a set of 5 numbers is 20. If 4 additional numbers are added to the set, the average increases to 24. What is the average of the additional 4 numbers?

A. 22
B. 25
C. 26
D. 28
E. 29

OA E

Solution:

Using the average formula: average = sum/number, we know the initial sum is 5 x 20 = 100. We can let x = the sum of the additional 4 numbers and create the equation:

(100 + x)/(5 + 4) = 24

(100 + x)/9 = 24

100 + x = 216

x = 116

The average of the 4 numbers is 116/4 = 29.

Answer: E

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