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# Working at their respective constant rates, machine I makes

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Working at their respective constant rates, machine I makes [#permalink]  04 Mar 2017, 03:52
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Question Stats:

91% (01:04) correct 8% (02:06) wrong based on 36 sessions

Working at their respective constant rates, machine I makes 240 copies in 8 minutes and machine II makes 240 copies in 5 minutes. At these rates, how many more copies does machine II make in 4 minutes than machine I makes in 6 minutes?

A) 10

B) 12

C) 15

D) 20

E) 24
[Reveal] Spoiler: OA

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Re: Working at their respective constant rates, machine I makes [#permalink]  09 Mar 2017, 19:30
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Explanation

Let the number of copies machine I makes in 6 minutes be x
$$\frac{copies}{minutes} = \frac{240}{8} = \frac{x}{6}$$

$$x= 180$$

Now find the number of copies made by machine II in 4 minutes: let it be y

$$\frac{copies}{minutes} = \frac{240}{5} = \frac{y}{4}$$

$$x= 192$$

How many more copies were made by machine II?

192 -180 = 12.

Hence option B is correct.
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Re: Working at their respective constant rates, machine I makes   [#permalink] 09 Mar 2017, 19:30
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