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

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

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25 Jun 2012, 09:32
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5% (low)

Question Stats:

92% (00:40) correct 8% (00:43) wrong based on 348 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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Re: A copy machine, working at a constant rate, makes 35 copies [#permalink]

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25 Jun 2012, 09:48
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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

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

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15 Nov 2012, 00:59
1
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$$Rate1+Rate2=CombinedRate$$
$$\frac{35}{1min}+\frac{55}{1min}=\frac{90}{1min}$$
$$\frac{90}{1min}(30min)=2,700$$copies

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

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30 Apr 2013, 00:01
why not 1/35 + 1/55 = 18/385 for 2 copies?

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

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30 Apr 2013, 00:50
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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, 16:09
darn did something stupid

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

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05 Jun 2013, 16:37
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

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

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07 Feb 2017, 02:17
Simple conception of work problem. If A makes 35/copies/min B makes 65/copies/min. Together each working independently they make 90 copies/min. Multiply 90 copies by 30 minutes to give you 2700 copies a minute.

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

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27 May 2017, 06:23
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

1st Copy machine's Rate, A = 35 copies per minute
2nd Copy Machine's Rate, B = 55 copies per minute

Working Together, means we can ADD THE RATES
Combined Rate, A+B= 35 + 55= 90 copies per minute
i.e 1 minute = 90 copies
or, 30 minutes (half an hour) =90 x 30 copies = 2700 Copies

[Reveal] Spoiler:
B

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

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27 May 2017, 08:40
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

$$(35+55)*30 = 2700$$

Thus, the correct answer will be (B)
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Re: A copy machine, working at a constant rate, makes 35 copies   [#permalink] 27 May 2017, 08:40
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