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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] New post 04 Mar 2017, 03:52
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Question Stats:

94% (01:12) correct 5% (02:06) wrong based on 54 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] New post 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] New post 08 Mar 2019, 10:32
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Carcass wrote:
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


We can also solve this question by applying some number/common sense

GIVEN: Machine I makes 240 copies in 8 minutes
So, Machine I makes 120 copies in 4 minutes [if you HALVE the work time, you HALVE the output]
And Machine I makes 60 copies in 2 minutes [if you HALVE the work time, you HALVE the output]
And Machine I makes 180 copies in 6 minutes [if you TRIPLE the work time, you TRIPLE the output]


GIVEN: Machine II makes 240 copies in 5 minutes
So, Machine II makes 48 copies in 1 minute [if you divide the work time BY FIVE, the output is divided BY FIVE]
And Machine II makes 192 copies in 6 minutes [if you QUADRUPLE the work time, the output is QUADRUPLED]


At these rates, how many more copies does machine II make in 4 minutes than machine I makes in 6 minutes?
Answer = 192 - 180
= 12

Answer: B

Cheers,
Brent
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Re: Working at their respective constant rates, machine I makes   [#permalink] 08 Mar 2019, 10:32
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