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# If the sum of n consecutive positive integers is 42, which of these co

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Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 7230
GMAT 1: 760 Q51 V42
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If the sum of n consecutive positive integers is 42, which of these co  [#permalink]

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12 Apr 2019, 01:39
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77% (01:54) correct 23% (02:07) wrong based on 44 sessions

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[GMAT math practice question]

If the sum of n consecutive positive integers is 42, which of these could be the value of n?

A. 7
B. 8
C. 9
D. 10
E. 11

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"Only $149 for 3 month Online Course" "Free Resources-30 day online access & Diagnostic Test" "Unlimited Access to over 120 free video lessons - try it yourself" Intern Joined: 09 Apr 2019 Posts: 1 Re: If the sum of n consecutive positive integers is 42, which of these co [#permalink] ### Show Tags 12 Apr 2019, 02:51 3+4+5+6+7+8+9 = 42 7 numbers - Option A CEO Joined: 18 Aug 2017 Posts: 3006 Location: India Concentration: Sustainability, Marketing GPA: 4 WE: Marketing (Energy and Utilities) If the sum of n consecutive positive integers is 42, which of these co [#permalink] ### Show Tags 12 Apr 2019, 02:55 MathRevolution wrote: [GMAT math practice question] If the sum of n consecutive positive integers is 42, which of these could be the value of n? A. 7 B. 8 C. 9 D. 10 E. 11 sum of consective no n*(n+1)/2 given n^2+n= 84 n^2+n-84=0 not able to get the answer from this relation other way let first integer ; x ; so next x+1 lets try for n=7 ; 7x+21= 42 x= 3 ; sufficient for other options we wont get integer value of x IMO A . I am not sure why answer is not coming from sum of consective no n*(n+1)/2 _________________ If you liked my solution then please give Kudos. Kudos encourage active discussions. Director Joined: 06 Jan 2015 Posts: 628 Location: India Concentration: Operations, Finance GPA: 3.35 WE: Information Technology (Computer Software) Re: If the sum of n consecutive positive integers is 42, which of these co [#permalink] ### Show Tags 12 Apr 2019, 03:04 Archit3110 wrote: MathRevolution wrote: [GMAT math practice question] If the sum of n consecutive positive integers is 42, which of these could be the value of n? A. 7 B. 8 C. 9 D. 10 E. 11 sum of consective no n*(n+1)/2 given n^2+n= 84 n^2+n-84=0 not able to get the answer from this relation other way let first integer ; x ; so next x+1 lets try for n=7 ; 7x+21= 42 x= 3 ; sufficient for other options we wont get integer value of x IMO A . I am not sure why answer is not coming from sum of consecutive no n*(n+1)/2 HI Archit3110 sum of consecutive no n*(n+1)/2 is for consecutive integers from n=1. But here we are not sure the consecutive integers are from n=1 or might be n=7 If you are adding Sum of consecutive integers of 100 then it would be 100*101/2 ==> 50*101 ==> 5050 _________________ आत्मनॊ मोक्षार्थम् जगद्धिताय च Resource: GMATPrep RCs With Solution CEO Joined: 18 Aug 2017 Posts: 3006 Location: India Concentration: Sustainability, Marketing GPA: 4 WE: Marketing (Energy and Utilities) Re: If the sum of n consecutive positive integers is 42, which of these co [#permalink] ### Show Tags 12 Apr 2019, 03:09 NandishSS okay understood thanks.. NandishSS wrote: Archit3110 wrote: MathRevolution wrote: [GMAT math practice question] If the sum of n consecutive positive integers is 42, which of these could be the value of n? A. 7 B. 8 C. 9 D. 10 E. 11 sum of consective no n*(n+1)/2 given n^2+n= 84 n^2+n-84=0 not able to get the answer from this relation other way let first integer ; x ; so next x+1 lets try for n=7 ; 7x+21= 42 x= 3 ; sufficient for other options we wont get integer value of x IMO A . I am not sure why answer is not coming from sum of consecutive no n*(n+1)/2 HI Archit3110 sum of consecutive no n*(n+1)/2 is for consecutive integers from n=1. But here we are not sure the consecutive integers are from n=1 or might be n=7 If you are adding Sum of consecutive integers of 100 then it would be 100*101/2 ==> 50*101 ==> 5050 _________________ If you liked my solution then please give Kudos. Kudos encourage active discussions. CEO Joined: 18 Aug 2017 Posts: 3006 Location: India Concentration: Sustainability, Marketing GPA: 4 WE: Marketing (Energy and Utilities) Re: If the sum of n consecutive positive integers is 42, which of these co [#permalink] ### Show Tags 12 Apr 2019, 04:11 [quote="Archit3110"]NandishSS okay understood thanks.. But trap would have been had question had both answer i.e with series starting from 1.. I feel it's ambiguous question ... Posted from my mobile device _________________ If you liked my solution then please give Kudos. Kudos encourage active discussions. VP Joined: 07 Dec 2014 Posts: 1179 If the sum of n consecutive positive integers is 42, which of these co [#permalink] ### Show Tags 12 Apr 2019, 08:38 MathRevolution wrote: [GMAT math practice question] If the sum of n consecutive positive integers is 42, which of these could be the value of n? A. 7 B. 8 C. 9 D. 10 E. 11 mean=sum/n if n is odd, mean 42/n must be integer only 7 divides into 42 A Math Revolution GMAT Instructor Joined: 16 Aug 2015 Posts: 7230 GMAT 1: 760 Q51 V42 GPA: 3.82 Re: If the sum of n consecutive positive integers is 42, which of these co [#permalink] ### Show Tags 14 Apr 2019, 18:39 1 => Recall that the sum of terms of an arithmetic sequence is $${\frac{(a+l)}{2}}*n$$ where a is the first term, $$l$$ is the last term and $$n$$ is the number of terms. We are told that $${\frac{(a+l)}{2}}*n = 42$$ or $$n(a+l) = 84.$$ Thus, $$n$$ is a factor of $$84$$. $$7$$ is the unique factor of $$84$$ among the choices. Therefore, the answer is A. Answer: A _________________ MathRevolution: Finish GMAT Quant Section with 10 minutes to spare The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy. "Only$149 for 3 month Online Course"
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Director
Joined: 06 Jan 2015
Posts: 628
Location: India
Concentration: Operations, Finance
GPA: 3.35
WE: Information Technology (Computer Software)
Re: If the sum of n consecutive positive integers is 42, which of these co  [#permalink]

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16 Apr 2019, 19:56
MathRevolution wrote:
[GMAT math practice question]

If the sum of n consecutive positive integers is 42, which of these could be the value of n?

A. 7
B. 8
C. 9
D. 10
E. 11

HI amanvermagmat, GMATGuruNY, pushpitkc Gladiator59 niks18

Any other method to solve these kind of problems?
_________________
आत्मनॊ मोक्षार्थम् जगद्धिताय च

Resource: GMATPrep RCs With Solution
Re: If the sum of n consecutive positive integers is 42, which of these co   [#permalink] 16 Apr 2019, 19:56
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