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If a1, a2, a3, . . . , an, . . . is a sequence such that an=2n for all
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Updated on: 06 Oct 2017, 07:48
Question Stats:
74% (01:31) correct 26% (01:39) wrong based on 171 sessions
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Tough and Tricky questions: Sequences. If a1, a2, a3, . . . , an, . . . is a sequence such that \(a_n=2n\) for all n ≥ 1, is \(a_i\) greater than \(a_j\) ? (1) i is odd and j is even (2) i^2 > j^2 Kudos for a correct solution.
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Originally posted by Bunuel on 18 Dec 2014, 06:51.
Last edited by Bunuel on 06 Oct 2017, 07:48, edited 2 times in total.
Added the OA.



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Re: If a1, a2, a3, . . . , an, . . . is a sequence such that an=2n for all
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18 Dec 2014, 07:47
1. Since we dont know the value of i and j it is difficult to judge the value a_i or a_j. Insufficient 2. i^2>j^2 i>j since sequence is valid only for +ve numbers we can ignore negative values so. a(i) always greater than a(j) for i>j since a(i)=2i and a(j)=2j.. Sufficient. Ans B
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Re: If a1, a2, a3, . . . , an, . . . is a sequence such that an=2n for all
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19 Dec 2014, 10:37
If a1, a2, a3, . . . , an, . . . is a sequence such that a_n=2n for all n ≥ 1, is a_i greater than a_j ? (1) i is odd and j is even (2) i^2 > j^2 Solution: Here each term is twice of previous term. Need to identify whether i > j? Statement 1: i is odd and j is even Doesn't provide any relation between i and j  Insufficient Statement 2: i^2 > j^2 Since a_i and a_j are terms of sequence, i and j must be positive integers. Thus i must be greater than j and hence Statement 2 alone is Sufficient. Answer B
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Re: If a1, a2, a3, . . . , an, . . . is a sequence such that an=2n for all
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22 Dec 2014, 07:50
Bunuel wrote: Tough and Tricky questions: Sequences. If a1, a2, a3, . . . , an, . . . is a sequence such that \(a_n=2n\) for all n ≥ 1, is \(a_i\) greater than \(a_j\) ? (1) i is odd and j is even (2) i^2 > j^2 Kudos for a correct solution.Since given that \(a_n = 2n\), for all \(n\geq{1}\) then: \(a_1=2*1=2\); \(a_2=2*2=4\); \(a_3=2*3=6\); \(a_4=2*4=8\); ... Basically we have a sequence of positive even numbers. Question asks whether \(a_i>a_j\)? So, it basically asks whether \(i>j\)? (1) i is add and j is even. Not sufficient. (2) i^2 > j^2 > since \(i\) and \(j\) are both positive integers (they represent index numbers) then \(i>j\). Sufficient. Answer: B.
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Re: If a1, a2, a3, . . . , an, . . . is a sequence such that an=2n for all
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06 Oct 2017, 07:46
The correct answer is Option B. Bunuel : please provide OA after review.



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Re: If a1, a2, a3, . . . , an, . . . is a sequence such that an=2n for all
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06 Oct 2017, 07:49
chipsy wrote: The correct answer is Option B. Bunuel : please provide OA after review. _____________________ Added the OA. Thank you.
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Re: If a1, a2, a3, . . . , an, . . . is a sequence such that an=2n for all
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18 Mar 2018, 02:06
Hi Bunuel please the question does not tell you if i or j is ≥ 1 and that is why i chose E.



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Re: If a1, a2, a3, . . . , an, . . . is a sequence such that an=2n for all
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18 Mar 2018, 05:51
chisichei wrote: Hi Bunuel please the question does not tell you if i or j is ≥ 1 and that is why i chose E. i and j are index numbers indicating which position a number has in the sequence. The sequence starts with a1, so both i and j must be more than or equal to 1.
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Re: If a1, a2, a3, . . . , an, . . . is a sequence such that an=2n for all
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22 May 2019, 04:19
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Re: If a1, a2, a3, . . . , an, . . . is a sequence such that an=2n for all
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