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# A certain list consists of 21 different numbers. If n is in

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A certain list consists of 21 different numbers. If n is in [#permalink]  31 Oct 2010, 03:06
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A certain list consists of 21 different numbers. If n is in the list and n is 4 times the average(arithmetic mean) of the other 20 numbers in the list, then n is what fraction of the sum of the 21 numbers in the list?

(A) 1/20
(B) 1/6
(C) 1/5
(D) 4/21
(E) 5/21
[Reveal] Spoiler: OA

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Last edited by monirjewel on 31 Oct 2010, 04:06, edited 1 time in total.
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Re: A certain list consists [#permalink]  31 Oct 2010, 07:08
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monirjewel wrote:
A certain list consists of 21 different numbers. If n is in the list and n is 4 times the average(arithmetic mean) of the other 20 numbers in the list, then n is what fraction of the sum of the 21 numbers in the list?

(A) 1/20
(B) 1/6
(C) 1/5
(D) 4/21
(E) 5/21

Given: average_{20}=\frac{sum_{20}}{20}=\frac{n}{4} --> sum_{20}=5n --> sum_{21}=sum_{20}+n=5n+n=6n;

Question: n is what fraction of the sum of the 21 numbers in the list?
\frac{n}{sum_{21}}=\frac{n}{6n}=\frac{1}{6}.

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Re: A certain list consists [#permalink]  09 Dec 2010, 04:03
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monirjewel wrote:
A certain list consists of 21 different numbers. If n is in the list and n is 4 times the average(arithmetic mean) of the other 20 numbers in the list, then n is what fraction of the sum of the 21 numbers in the list?

(A) 1/20
(B) 1/6
(C) 1/5
(D) 4/21
(E) 5/21

When you have your answer in percentages/fractions and there are no values in the data given to you, assume values.
Here you do not have the value of any number. So assume 20 numbers are all 1. Their average is 1 and sum is 20.
Then n is 4 and sum of 21 numbers is 24.
4/24 = 1/6
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Save $100 on Veritas Prep GMAT Courses And Admissions Consulting Enroll now. Pay later. Take advantage of Veritas Prep's flexible payment plan options. Veritas Prep Reviews Manager Status: Bunuel's fan! Joined: 08 Jul 2011 Posts: 238 Followers: 0 Kudos [?]: 17 [0], given: 55 Re: A certain list consists [#permalink] 09 Apr 2013, 08:02 VeritasPrepKarishma wrote: monirjewel wrote: A certain list consists of 21 different numbers. If n is in the list and n is 4 times the average(arithmetic mean) of the other 20 numbers in the list, then n is what fraction of the sum of the 21 numbers in the list? (A) 1/20 (B) 1/6 (C) 1/5 (D) 4/21 (E) 5/21 When you have your answer in percentages/fractions and there are no values in the data given to you, assume values. Here you do not have the value of any number. So assume 20 numbers are all 1. Their average is 1 and sum is 20. Then n is 4 and sum of 21 numbers is 24. 4/24 = 1/6 For this solution, I thought all numbers have to be different? Veritas Prep GMAT Instructor Joined: 16 Oct 2010 Posts: 4761 Location: Pune, India Followers: 1112 Kudos [?]: 5037 [2] , given: 164 Re: A certain list consists [#permalink] 09 Apr 2013, 22:18 2 This post received KUDOS Expert's post gmatfighter12 wrote: VeritasPrepKarishma wrote: monirjewel wrote: A certain list consists of 21 different numbers. If n is in the list and n is 4 times the average(arithmetic mean) of the other 20 numbers in the list, then n is what fraction of the sum of the 21 numbers in the list? (A) 1/20 (B) 1/6 (C) 1/5 (D) 4/21 (E) 5/21 When you have your answer in percentages/fractions and there are no values in the data given to you, assume values. Here you do not have the value of any number. So assume 20 numbers are all 1. Their average is 1 and sum is 20. Then n is 4 and sum of 21 numbers is 24. 4/24 = 1/6 For this solution, I thought all numbers have to be different? It usually doesn't matter if the numbers don't need to be integers. The numbers could be 0.999999999999999, 0.99999998, 1.00000000000000001, 1.000000000002 etc. Effectively, they are all 1 and our solution doesn't change at all. _________________ Karishma Veritas Prep | GMAT Instructor My Blog Save$100 on Veritas Prep GMAT Courses And Admissions Consulting
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A certain list consists of 21 different numbers. If n is in the [#permalink]  04 May 2013, 12:22
udaymathapati wrote:
A certain list consists of 21 different numbers. If n is in the list and n is 4 times the average (arithmetic mean) of the other 20 numbers in the list, then n is what fraction of the sum of the 21 numbers in the list?
A. 201
B. 61
C. 51
D. 214
E. 215

Umm 1/6 does seem the answer...udaymathapati could u please confirm the answer and change the choices? well 201 or 61 are not really the proper fractions the question expects.

Regards,
Arpan
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Re: A certain list consists of 21 different numbers. If n is in  [#permalink]  05 May 2013, 03:40
Expert's post
arpanpatnaik wrote:
udaymathapati wrote:
A certain list consists of 21 different numbers. If n is in the list and n is 4 times the average (arithmetic mean) of the other 20 numbers in the list, then n is what fraction of the sum of the 21 numbers in the list?
A. 201
B. 61
C. 51
D. 214
E. 215

Umm 1/6 does seem the answer...udaymathapati could u please confirm the answer and change the choices? well 201 or 61 are not really the proper fractions the question expects.

Regards,
Arpan

Merging topics. Check here: a-certain-list-consists-of-21-different-numbers-if-n-is-in-103995.html#p810467
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Re: A certain list consists of 21 different numbers. If n is in [#permalink]  04 Nov 2013, 08:00
This Qs appeared in the newly launched GMAT Exam Prep -1.
GMAC said these Qs were never seen before. What a blatant lie!!!
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Re: A certain list consists [#permalink]  04 Nov 2013, 14:34
VeritasPrepKarishma wrote:
monirjewel wrote:
A certain list consists of 21 different numbers. If n is in the list and n is 4 times the average(arithmetic mean) of the other 20 numbers in the list, then n is what fraction of the sum of the 21 numbers in the list?

(A) 1/20
(B) 1/6
(C) 1/5
(D) 4/21
(E) 5/21

When you have your answer in percentages/fractions and there are no values in the data given to you, assume values.
Here you do not have the value of any number. So assume 20 numbers are all 1. Their average is 1 and sum is 20.
Then n is 4 and sum of 21 numbers is 24.
4/24 = 1/6

Waoo thank you! It is a really usufull method!

Thank you!
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Re: A certain list consists of 21 different numbers. If n is in [#permalink]  05 Nov 2013, 08:13
1
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monirjewel wrote:
A certain list consists of 21 different numbers. If n is in the list and n is 4 times the average(arithmetic mean) of the other 20 numbers in the list, then n is what fraction of the sum of the 21 numbers in the list?

(A) 1/20
(B) 1/6
(C) 1/5
(D) 4/21
(E) 5/21

This is a PS question placed in the DS forum. Please relocate accordingly.
Math Expert
Joined: 02 Sep 2009
Posts: 29655
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Kudos [?]: 26248 [0], given: 2707

Re: A certain list consists of 21 different numbers. If n is in [#permalink]  05 Nov 2013, 08:22
Expert's post
gdediegoi wrote:
monirjewel wrote:
A certain list consists of 21 different numbers. If n is in the list and n is 4 times the average(arithmetic mean) of the other 20 numbers in the list, then n is what fraction of the sum of the 21 numbers in the list?

(A) 1/20
(B) 1/6
(C) 1/5
(D) 4/21
(E) 5/21

This is a PS question placed in the DS forum. Please relocate accordingly.

________
Done. Thank you.
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Re: A certain list consists of 21 different numbers. If n is in [#permalink]  30 Dec 2013, 13:17
1
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monirjewel wrote:
A certain list consists of 21 different numbers. If n is in the list and n is 4 times the average(arithmetic mean) of the other 20 numbers in the list, then n is what fraction of the sum of the 21 numbers in the list?

(A) 1/20
(B) 1/6
(C) 1/5
(D) 4/21
(E) 5/21

n = 4x

where 'x' is the average of other 20 numbers

Then sum of other 20 numbers is 20x

So we get 4x/24x = 1/6

Cheers!
J
Re: A certain list consists of 21 different numbers. If n is in   [#permalink] 30 Dec 2013, 13:17
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# A certain list consists of 21 different numbers. If n is in

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