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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
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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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Difficulty:

15% (low)

Question Stats:

79% (01:43) correct 21% (01:47) wrong based on 143 sessions

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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 t?

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

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"Only $79 for 1 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: 7960 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 4 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 _________________ Ask GMAT Experts Forum Moderator Status: Preparing for GMAT Joined: 25 Nov 2015 Posts: 1043 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 2 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... VP Joined: 07 Dec 2014 Posts: 1222 Re: 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: 8011 GMAT 1: 760 Q51 V42 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 1 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]

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15 Sep 2018, 04:07
1
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

Dear Moderator,
There seems to be a small typo here. Variable K has been mistakenly written instead of variable t. Hope you will look into this. Thank you.
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- Stne
Math Expert
Joined: 02 Sep 2009
Posts: 58427
Re: There are 3 machines with the same work rate. If it took t hours for 3  [#permalink]

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15 Sep 2018, 04:12
stne wrote:
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

Dear Moderator,
There seems to be a small typo here. Variable K has been mistakenly written instead of variable t. Hope you will look into this. Thank you.

_______________
Edited. Thank you.
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Re: There are 3 machines with the same work rate. If it took t hours for 3  [#permalink]

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15 Sep 2018, 08:05
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 t?

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

Let efficiency of each machine be "e"

So, $$3*e*t = 2*e*(t+2)$$

Or, $$3t = 2t + 4$$

Or, $$t = 4$$, Answer must be (A) 4
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Re: There are 3 machines with the same work rate. If it took t hours for 3  [#permalink]

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01 Oct 2018, 06:46
t/t+2=2/3
So, 3t=2t+4
=> t=4 hrs.
(A)
Re: There are 3 machines with the same work rate. If it took t hours for 3   [#permalink] 01 Oct 2018, 06:46
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