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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
Followers: 0

Kudos [?]: 4 [0], given: 8

A copy machine, working at a constant rate, makes 35 copies [#permalink]  25 Jun 2012, 08:32
00:00

Difficulty:

5% (low)

Question Stats:

91% (01:43) correct 9% (00:43) wrong based on 186 sessions
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
Math Expert
Joined: 02 Sep 2009
Posts: 31223
Followers: 5341

Kudos [?]: 62027 [4] , given: 9426

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

_________________
Senior Manager
Joined: 13 Aug 2012
Posts: 464
Concentration: Marketing, Finance
GMAT 1: Q V0
GPA: 3.23
Followers: 19

Kudos [?]: 320 [1] , given: 11

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

_________________

Impossible is nothing to God.

Intern
Joined: 24 Sep 2012
Posts: 7
GMAT Date: 09-08-2013
GPA: 3.5
Followers: 0

Kudos [?]: 0 [0], given: 0

Re: A copy machine, working at a constant rate, makes 35 copies [#permalink]  29 Apr 2013, 23:01
why not 1/35 + 1/55 = 18/385 for 2 copies?
Math Expert
Joined: 02 Sep 2009
Posts: 31223
Followers: 5341

Kudos [?]: 62027 [1] , given: 9426

Re: A copy machine, working at a constant rate, makes 35 copies [#permalink]  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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Manager
Joined: 24 Apr 2013
Posts: 54
Schools: Duke '16
Followers: 0

Kudos [?]: 6 [0], given: 76

Re: A copy machine, working at a constant rate, makes 35 copies [#permalink]  07 May 2013, 15:09
darn did something stupid
Current Student
Joined: 30 May 2013
Posts: 11
GMAT 1: 680 Q48 V35
Followers: 0

Kudos [?]: 2 [0], given: 2

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