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# There are 3 machines with the same work rate. If it took t hours for 3

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Math Revolution GMAT Instructor
Joined: 16 Aug 2015
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GMAT 1: 800 Q59 V59
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There are 3 machines with the same work rate. If it took t hours for 3 [#permalink]

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24 Oct 2017, 07:54
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[GMAT math practice question]

There are 3 machines with the same work rate. If it took t hours for 3 machines to work and took t+2 hours for 2 machines when working together, what is the value of k?

A. 4
B. 5
C. 6
D. 7
E. 9

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"Only $79 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 Expert Joined: 02 Aug 2009 Posts: 5784 Re: There are 3 machines with the same work rate. If it took t hours for 3 [#permalink] ### Show Tags 24 Oct 2017, 08:08 2 This post received KUDOS Expert's post MathRevolution wrote: [GMAT math practice question] There are 3 machines with the same work rate. If it took t hours for 3 machines to work and took t+2 hours for 2 machines when working together, what is the value of k? A. 4 B. 5 C. 6 D. 7 E. 9 I am sure Q is asking value of t and k is a typo error.. speed si the same.. if 3 do it in t hours, ONE will do it in 3*t.. if 2 do it in t+2 hours, ONE will do it in 2*(t+2)=2t+4.. But the speed is SAME, so 3t=2t+4....t=4 A _________________ Absolute modulus :http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372 Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html GMAT online Tutor Director Status: Preparing for GMAT Joined: 25 Nov 2015 Posts: 629 Location: India GPA: 3.64 Re: There are 3 machines with the same work rate. If it took t hours for 3 [#permalink] ### Show Tags 24 Oct 2017, 08:38 The rate of work of each machine is the same. Work done by 3 machines in 1 hr = $$\frac{1}{t}$$ Work done by 1 machine in 1 hr = $$\frac{1}{{3t}}$$ Work done by 2 machines in 1 hr = $$\frac{2}{{3t}}$$ = $$\frac{1}{{t+2}}$$ $$\frac{2}{{3t}}$$=$$\frac{1}{{t+2}}$$ 2t+4=3t t=4 Answer A Please give kudos, if u liked my post! _________________ Please give kudos, if you like my post When the going gets tough, the tough gets going... Director Joined: 07 Dec 2014 Posts: 999 There are 3 machines with the same work rate. If it took t hours for 3 [#permalink] ### Show Tags 24 Oct 2017, 13:31 There are 3 machines with the same work rate. If it took t hours for 3 machines to work and took t+2 hours for 2 machines when working together, what is the value of k? A. 4 B. 5 C. 6 D. 7 E. 9 2/3 rate➡3/2 time 3/2*t=t+2 t=4 hours A Math Revolution GMAT Instructor Joined: 16 Aug 2015 Posts: 5452 GMAT 1: 800 Q59 V59 GPA: 3.82 Re: There are 3 machines with the same work rate. If it took t hours for 3 [#permalink] ### Show Tags 26 Oct 2017, 00:46 => Assume X is the time one machine takes to work. 1/T=3/X and 1/T+2=2/X X = 3T and X = 2(T+2). We have 3T = 2T + 4 or T = 4. Thus, 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$79 for 3 month Online Course"
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Re: There are 3 machines with the same work rate. If it took t hours for 3   [#permalink] 26 Oct 2017, 00:46
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