The average of 5 numbers is 6.8. If one of the numbers is

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BTGmoderatorDC: Moderator; Posts: 7187; Joined: Thu Sep 07, 2017 4:43 pm; Followed by:23 members

The average of 5 numbers is 6.8. If one of the numbers is

by BTGmoderatorDC » Wed Aug 21, 2019 5:34 pm

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The average of 5 numbers is 6.8. If one of the numbers is multiplied by a factor of 3, the average of the numbers increases to 9.2. What number is multiplied by 3?

(A) 1.5
(B) 3.0
(C) 3.9
(D) 4.0
(E) 6.0

OA E

Source: Veritas Prep

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Source: Beat The GMAT — Problem Solving | Wed Aug 21, 2019 5:34 pm

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Jay@ManhattanReview: GMAT Instructor; Posts: 3008; Joined: Mon Aug 22, 2016 6:19 am; Location: Grand Central / New York; Thanked: 470 times; Followed by:34 members

by Jay@ManhattanReview » Wed Aug 21, 2019 8:39 pm

BTGmoderatorDC wrote:The average of 5 numbers is 6.8. If one of the numbers is multiplied by a factor of 3, the average of the numbers increases to 9.2. What number is multiplied by 3?

(A) 1.5
(B) 3.0
(C) 3.9
(D) 4.0
(E) 6.0

OA E

Source: Veritas Prep

Given that the average of 5 numbers is 6.8, the sum of the numbers = 5*6.8 = 34. Say x is one of the numbers that is multiplied by a factor 3. Thus, the new sum of the 5 numbers = 34 - x + 3x = 34 + 2x

Thus, the revised average of the 5 numbers = (34 + 2x)/5 = 9.2 => x = 6

The correct answer: E

Hope this helps!

-Jay
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GMATGuruNY: GMAT Instructor; Posts: 15539; Joined: Tue May 25, 2010 12:04 pm; Location: New York, NY; Thanked: 13060 times; Followed by:1906 members; GMAT Score:790

average

by GMATGuruNY » Thu Aug 22, 2019 1:59 am

BTGmoderatorDC wrote:The average of 5 numbers is 6.8. If one of the numbers is multiplied by a factor of 3, the average of the numbers increases to 9.2. What number is multiplied by 3?

(A) 1.5
(B) 3.0
(C) 3.9
(D) 4.0
(E) 6.0

Sum of the original 5 numbers = (count)(average) = (5)(6.8) = 34
Sum of the resulting 5 numbers = (count)(average) = (5)(9.2) = 46
Increase in the sum = 46-24 = 12
Since this increase of 12 is yielded by multiplying one of the numbers by 3, 12 must be equal to the difference between the number tripled and the original number:
12 = 3x - x
12 = 2x
x = 6

The correct answer is E.

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Scott@TargetTestPrep: GMAT Instructor; Posts: 8086; Joined: Sat Apr 25, 2015 10:56 am; Location: Los Angeles, CA; Thanked: 43 times; Followed by:29 members

by Scott@TargetTestPrep » Sat Aug 24, 2019 4:17 am

BTGmoderatorDC wrote:The average of 5 numbers is 6.8. If one of the numbers is multiplied by a factor of 3, the average of the numbers increases to 9.2. What number is multiplied by 3?

(A) 1.5
(B) 3.0
(C) 3.9
(D) 4.0
(E) 6.0

OA E

Source: Veritas Prep

The sum of the original 5 numbers is 6.8 x 5 = 34.

If we let k = the number that is multiplied by a factor of 3, then the new sum is 34 - k + 3k = 34 + 2k. We can create the equation:

(34 + 2k)/5 = 9.2

34 + 2k = 46

2k = 12

k = 6

Answer: E

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