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# Is n an odd number?

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Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 6227
GMAT 1: 760 Q51 V42
GPA: 3.82
Is n an odd number?  [#permalink]

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04 Sep 2018, 00:24
00:00

Difficulty:

55% (hard)

Question Stats:

44% (01:04) correct 56% (01:00) wrong based on 57 sessions

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[Math Revolution GMAT math practice question]

Is n an odd number?

1) n is the sum of 2 prime numbers
2) n is a multiple of 11

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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 $99 for 3 month Online Course" "Free Resources-30 day online access & Diagnostic Test" "Unlimited Access to over 120 free video lessons - try it yourself"  Math Revolution Discount Codes Manhattan GMAT Discount Codes Optimus Prep Discount Codes Director Joined: 20 Feb 2015 Posts: 733 Concentration: Strategy, General Management Re: Is n an odd number? [#permalink] ### Show Tags 04 Sep 2018, 00:40 MathRevolution wrote: [Math Revolution GMAT math practice question] Is n an odd number? 1) n is the sum of 2 prime numbers 2) n is a multiple of 11 1) n is the sum of 2 prime numbers n=2+3=5 =odd n=3+5=8=even insufficient 2) n is a multiple of 11 n=22,33,44 insufficient using both n=22=3+19 = even n=33=2+31=odd insufficient E Director Status: Learning stage Joined: 01 Oct 2017 Posts: 856 WE: Supply Chain Management (Energy and Utilities) Re: Is n an odd number? [#permalink] ### Show Tags 04 Sep 2018, 00:43 1 MathRevolution wrote: [Math Revolution GMAT math practice question] Is n an odd number? 1) n is the sum of 2 prime numbers 2) n is a multiple of 11 Question stem:- Is n an odd number? St1:- n is the sum of 2 prime numbers a) n=2+3=5, which is odd b)n=3+5=8, which is even Insufficient. St2:- n is a multiple of 11 Or, n=11k, where k is a positive integer a)when k=1, n=11, which is odd. b) when k=2, n=22, which is even. Insufficient. Combined, n is the sum of 2 prime numbers and n is multiple of 11. a) n=19+3=22 and n=11*2=22, which is even b) n=119+2=121 and n=11*11=121, which is odd. Insufficient. Ans. (E) _________________ Regards, PKN Rise above the storm, you will find the sunshine GMATH Teacher Status: GMATH founder Joined: 12 Oct 2010 Posts: 195 Re: Is n an odd number? [#permalink] ### Show Tags 04 Sep 2018, 18:41 MathRevolution wrote: [Math Revolution GMAT math practice question] Is n an odd number? 1) n is the sum of 2 prime numbers 2) n is a multiple of 11 Is n odd ? (1+2) Insufficient: > Take n = 22 = 3+19 to answer in the negative > Take n = 33 = 2+31 to answer in the positive The above follows the notations and rationale taught in the GMATH method. Regards, fskilnik. _________________ Fabio Skilnik :: http://www.GMATH.net (Math for the GMAT) Course release PROMO : finish our test drive till 30/Sep with (at least) 60 correct answers out of 92 (12-questions Mock included) to gain a 70% discount! Math Revolution GMAT Instructor Joined: 16 Aug 2015 Posts: 6227 GMAT 1: 760 Q51 V42 GPA: 3.82 Re: Is n an odd number? [#permalink] ### Show Tags 06 Sep 2018, 01:32 => Forget conventional ways of solving math questions. For DS problems, the VA (Variable Approach) method is the quickest and easiest way to find the answer without actually solving the problem. Remember that equal numbers of variables and independent equations ensure a solution. Since we have 1 variable (n) and 0 equations, D is most likely to be the answer. So, we should consider each of the conditions on their own first. Condition 1) If $$n = 2 + 3$$, then $$n = 5$$ is odd and the answer is ‘yes’. If $$n = 3 + 5$$, then $$n = 8$$ is even and the answer is ‘no’. Since we don’t have a unique solution, condition 1) is not sufficient. Condition 2) If $$n = 11$$, then n is odd and the answer is ‘yes’. If $$n = 22$$, then n is even and the answer is ‘no’. Since we don’t have a unique solution, condition 2) is not sufficient. Conditions 1) & 2) If $$n = 2 + 31$$, then $$n = 33$$ is odd and the answer is ‘yes’. If $$n = 13 + 31$$, then $$n = 44$$ is even and the answer is ‘no’ Since we don’t have a unique solution, both conditions 1) and 2) are not sufficient, when taken together. Therefore, E is the answer. Answer: E If the original condition includes “1 variable”, or “2 variables and 1 equation”, or “3 variables and 2 equations” etc., one more equation is required to answer the question. If each of conditions 1) and 2) provide an additional equation, there is a 59% chance that D is the answer, a 38% chance that A or B is the answer, and a 3% chance that the answer is C or E. Thus, answer D (conditions 1) and 2), when applied separately, are sufficient to answer the question) is most likely, but there may be cases where the answer is A,B,C or E. _________________ 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$99 for 3 month Online Course"
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Re: Is n an odd number? &nbs [#permalink] 06 Sep 2018, 01:32
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