A copy machine, working at a constant rate, makes 35 copies : GMAT Problem Solving (PS)
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# A copy machine, working at a constant rate, makes 35 copies

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Intern
Joined: 26 May 2012
Posts: 9
GMAT Date: 07-04-2012
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Kudos [?]: 5 [0], given: 8

A copy machine, working at a constant rate, makes 35 copies [#permalink]

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25 Jun 2012, 08:32
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Difficulty:

5% (low)

Question Stats:

92% (01:42) correct 8% (00:42) wrong based on 241 sessions

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A copy machine, working at a constant rate, makes 35 copies per minute. A second copy machine, working at a constant rate, makes 55 copies per minute. Working together at their respective rates, how many copies do the two machines make in half an hour ?

A. 90
B. 2,700
C. 4,500
D. 5,400
E. 324,000
[Reveal] Spoiler: OA
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Joined: 02 Sep 2009
Posts: 36638
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Kudos [?]: 93664 [4] , given: 10583

Re: A copy machine, working at a constant rate, makes 35 copies [#permalink]

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25 Jun 2012, 08:48
4
KUDOS
Expert's post
A copy machine, working at a constant rate, makes 35 copies per minute. A second copy machine, working at a constant rate, makes 55 copies per minute. Working together at their respective rates, how many copies do the two machines make in half an hour ?

A. 90
B. 2,700
C. 4,500
D. 5,400
E. 324,000

Together the two machines make 35+55=90 copies per minute. So, in half an hour they will make 90*30=2,700 copies.

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Kudos [?]: 434 [1] , given: 11

Re: A copy machine, working at a constant rate, makes 35 copies [#permalink]

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14 Nov 2012, 23:59
1
KUDOS
$$Rate1+Rate2=CombinedRate$$
$$\frac{35}{1min}+\frac{55}{1min}=\frac{90}{1min}$$
$$\frac{90}{1min}(30min)=2,700$$copies

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Re: A copy machine, working at a constant rate, makes 35 copies [#permalink]

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29 Apr 2013, 23:01
why not 1/35 + 1/55 = 18/385 for 2 copies?
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Kudos [?]: 93664 [1] , given: 10583

Re: A copy machine, working at a constant rate, makes 35 copies [#permalink]

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29 Apr 2013, 23:50
1
KUDOS
Expert's post
shahebali wrote:
why not 1/35 + 1/55 = 18/385 for 2 copies?

1/35 minutes is the time the first machine needs to make one copy.
1/55 minutes is the time the second machine needs to make one copy.

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Re: A copy machine, working at a constant rate, makes 35 copies [#permalink]

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07 May 2013, 15:09
darn did something stupid
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Joined: 30 May 2013
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Re: A copy machine, working at a constant rate, makes 35 copies [#permalink]

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05 Jun 2013, 15:37
Machine A = 35 copies per minute. 35*30 = 1050 copies in 30 minutes
Machine B = 55 copies per minute. 55*30 = 1650 copies in 30 minutes
1050+1650 = 2700 copies in 30 mins
Re: A copy machine, working at a constant rate, makes 35 copies   [#permalink] 05 Jun 2013, 15:37
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