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# There is a sequence of r, t, s, 1, 4, 3, 8, 15, 26. Each number of the

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Math Revolution GMAT Instructor
Joined: 16 Aug 2015
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There is a sequence of r, t, s, 1, 4, 3, 8, 15, 26. Each number of the  [#permalink]

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08 Aug 2017, 18:10
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15% (low)

Question Stats:

84% (01:41) correct 16% (02:14) wrong based on 72 sessions

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There is a sequence of r, t, s, 1, 4, 3, 8, 15, 26. Each number of the sequence is the sum of the 3 previous numbers. r=?

A. -2
B. -1
C. 0
D. 1
E. 2

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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" Senior PS Moderator Joined: 26 Feb 2016 Posts: 3386 Location: India GPA: 3.12 Re: There is a sequence of r, t, s, 1, 4, 3, 8, 15, 26. Each number of the [#permalink] ### Show Tags 08 Aug 2017, 20:02 MathRevolution wrote: There is a sequence of r, t, s, 1, 4, 3, 8, 15, 26. Each number of the sequence is the sum of the 3 previous numbers. r=? A. -2 B. -1 C. 0 D. 1 E. 2 This sequence is possible when r = -2, s = 5, t = -2 as r+s+t = 1. To double check whether the numbers we have selected are correct, we also have s + t + 1 = 4 to prove that the numbers chosen are correct. Hence, it is clear that Option A(r = -2) is our correct answer. _________________ You've got what it takes, but it will take everything you've got Director Joined: 04 Dec 2015 Posts: 750 Location: India Concentration: Technology, Strategy Schools: ISB '19, IIMA , IIMB, XLRI WE: Information Technology (Consulting) Re: There is a sequence of r, t, s, 1, 4, 3, 8, 15, 26. Each number of the [#permalink] ### Show Tags 08 Aug 2017, 23:18 MathRevolution wrote: There is a sequence of r, t, s, 1, 4, 3, 8, 15, 26. Each number of the sequence is the sum of the 3 previous numbers. r=? A. -2 B. -1 C. 0 D. 1 E. 2 We can solve this question by solving from last right number. Given Each number of the sequence is the sum of the $$3$$ previous numbers.Therefore; $$26 = (15 + 8 + 3) => 26$$ $$15 = (8 + 3 + 4) => 15$$ $$8 = (3 + 4 + 1) => 8$$ $$3 = (4 + 1 + s) => 5 + s$$ $$s = 3 - 5 => -2$$ $$4 = (1 + s + t)$$ $$4 = 1 - 2 + t => -1 + t$$ $$t = 4 + 1 => 5$$ $$1 = (s + t + r)$$ $$1 = -2 + 5 + r => 3 + r$$ $$r = 1 - 3 => -2$$ Answer (A)... _________________ Please Press "+1 Kudos" to appreciate. Math Revolution GMAT Instructor Joined: 16 Aug 2015 Posts: 7224 GMAT 1: 760 Q51 V42 GPA: 3.82 Re: There is a sequence of r, t, s, 1, 4, 3, 8, 15, 26. Each number of the [#permalink] ### Show Tags 10 Aug 2017, 01:14 ==> You get r+t+s=1, from t+s+1=4, you get t+s=3, and from r+t+s=r+3=1, you get r=1-3=-2. 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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Re: There is a sequence of r, t, s, 1, 4, 3, 8, 15, 26. Each number of the  [#permalink]

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13 Aug 2017, 12:25
r,s,t,1,4,3,8,1,5,26
3= 4+1+t , t=-2
4=1+(-2)+s, s=5
1=r+5+(-2) , r=-2
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Re: There is a sequence of r, t, s, 1, 4, 3, 8, 15, 26. Each number of the   [#permalink] 13 Aug 2017, 12:25
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