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# There are 4 machines with the same work rate. If it took k hours for 3

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Math Revolution GMAT Instructor
Joined: 16 Aug 2015
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There are 4 machines with the same work rate. If it took k hours for 3  [#permalink]

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01 Mar 2018, 03:50
00:00

Difficulty:

35% (medium)

Question Stats:

70% (01:51) correct 30% (01:52) wrong based on 100 sessions

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[GMAT math practice question]

There are 4 machines with the same work rate. If it took $$k$$ hours for 3 machines to work and did $$k-2$$ hours for 4 machines when working together, what is the value of $$k$$?

A. 4
B. 5
C. 6
D. 7
E. 8

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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" Intern Joined: 19 Feb 2018 Posts: 5 Re: There are 4 machines with the same work rate. If it took k hours for 3 [#permalink] ### Show Tags 01 Mar 2018, 05:33 1 2 If it takes 3 machines khours to work and 4 machine (k-2)hrs, then 1 machine will work in 3k hours which is also equivalent to 4(k-2) hours Therefore 3k=4k-8 K=8 Sent from my [device_name] using [url]GMAT Club Forum mobile app[/url] Math Revolution GMAT Instructor Joined: 16 Aug 2015 Posts: 8017 GMAT 1: 760 Q51 V42 GPA: 3.82 Re: There are 4 machines with the same work rate. If it took k hours for 3 [#permalink] ### Show Tags 04 Mar 2018, 19:25 => Work Amount = Number of machines * Work Rate * Time If r is the machine’s work rate, we have $$3rk = 4r(k-2)$$ or $$3k = 4k -8$$. Thus $$k = 8$$. Therefore, E is the answer. Answer: 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$79 for 1 month Online Course"
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Re: There are 4 machines with the same work rate. If it took k hours for 3  [#permalink]

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10 Jun 2019, 19:24
1
MathRevolution wrote:
[GMAT math practice question]

There are 4 machines with the same work rate. If it took $$k$$ hours for 3 machines to work and did $$k-2$$ hours for 4 machines when working together, what is the value of $$k$$?

A. 4
B. 5
C. 6
D. 7
E. 8

Let the rate of each machine be r. We can create the equation:

(3r)k = (4r)(k - 2)

3k = 4k - 8

8 = k

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Re: There are 4 machines with the same work rate. If it took k hours for 3   [#permalink] 10 Jun 2019, 19:24
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