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If a copier makes 3 copies every 4 seconds, then continues

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by AAPL » Mon Apr 09, 2018 5:37 am
If a copier makes 3 copies avery 4 seconds, then continues at this rate, how many minutes will it take to make 9,000 copies?

A. 60
B. 100
C. 120
D. 200
E. 3,000

The OA is D.

(#copies) / (seconds)

Let x = seconds to make 9,000 copies.

We get 3/4 = 9,000/x.

Cross multiply to get: 3x = (4)(9000)
Simplify: 3x = 36,000
Solve: x = 12,000 SECONDS

There are 60 seconds in a minute.
12,000/60 = 200
So, it takes 200 MINUTES to make 9000 copies. Option D.

Has anyone another strategic approach to solve this PS question? Regards!
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If a copier makes 3 copies every 4 seconds, then continues

by Brent@GMATPrepNow » Mon Apr 09, 2018 6:18 am
AAPL wrote:If a copier makes 3 copies avery 4 seconds, then continues at this rate, how many minutes will it take to make 9,000 copies?

A. 60
B. 100
C. 120
D. 200
E. 3,000

The OA is D.

(#copies) / (seconds)

Let x = seconds to make 9,000 copies.

We get 3/4 = 9,000/x.

Cross multiply to get: 3x = (4)(9000)
Simplify: 3x = 36,000
Solve: x = 12,000 SECONDS

There are 60 seconds in a minute.
12,000/60 = 200
So, it takes 200 MINUTES to make 9000 copies. Option D.

Has anyone another strategic approach to solve this PS question? Regards!
The above solution is perfect, but here's another approach...
We can apply some number sense in a series of steps

GIVEN: Copier makes 3 copies every 4 seconds
So: the copier makes 45 copies every 60 seconds [if we increase the working time by a factor of 15, then the number of copies increases by a factor of 15]
In other words, the copier makes 45 copies every 1 MINUTE [60 seconds = 1 MINUTE]
Keep going: the copier makes 9000 copies every 200 MINUTES [if we increase the working time by a factor of 200, then the number of copies increases by a factor of 200]

Answer: D

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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by Scott@TargetTestPrep » Wed Apr 11, 2018 5:41 am
AAPL wrote:If a copier makes 3 copies avery 4 seconds, then continues at this rate, how many minutes will it take to make 9,000 copies?

A. 60
B. 100
C. 120
D. 200
E. 3,000
The rate of the copy machine is:

3/4 copies per second or 3/(4/60) = 180/4 = 45 copies/minute

So it will take 9000/45 = 200 minutes to produce 9000 copies.

Alternate Solution:

We can create a proportion: 3 copies in 4 seconds equals 9000 copies in x seconds:

3/4 = 9000/x

3x = 36,000

x = 12,000 seconds

Since there are 60 seconds in a minute, we see that 12,000 seconds = 200 minutes.

Answer: D

Scott Woodbury-Stewart
Founder and CEO
[email protected]

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