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One machine, working at a constant rate, can fill a certain

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by swerve » Tue Aug 21, 2018 10:17 am

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Answers

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B

C

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E

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Difficulty—

One machine, working at a constant rate, can fill a production order in 8 hours. How long would it take four identical machines, working at the same constant rate, to fill the order?

A. 2 hours
B. 4 hours
C. 8 hours
D. 16 hours
E. 32 hours

The OA is A.

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by fskilnik@GMATH » Tue Aug 21, 2018 10:33 am
<p>
swerve wrote:</p>
One machine, working at a constant rate, can fill a production order in 8 hours. How long would it take four identical machines, working at the same constant rate, to fill the order?

A. 2 hours
B. 4 hours
C. 8 hours
D. 16 hours
E. 32 hours
It suffices to apply the generalization of the "taps shortcut", valid for any (finite) number of "taps".
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The solution above follows the notations and rationale taught in the <b>GMATH</b> method.
Fabio Skilnik :: GMATH method creator ( Math for the GMAT)
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One machine, working at a constant rate, can fill a certain

by Brent@GMATPrepNow » Tue Aug 21, 2018 10:53 am
swerve wrote:One machine, working at a constant rate, can fill a production order in 8 hours. How long would it take four identical machines, working at the same constant rate, to fill the order?

A. 2 hours
B. 4 hours
C. 8 hours
D. 16 hours
E. 32 hours

The OA is A.

Source: Veritas Prep
Let's assign a "nice" value to the entire job (a value that works well with the given information)

Let's say the machine is making widgets and an order = 8 widgets.

One machine, working at a constant rate, can fill a production order in 8 hours.
In other words, ONE machine can make 8 widgets in 8 hours
This means, ONE machine makes 1 widget per hour

How long would it take four machines to fill the order?
If ONE machine makes 1 widget in ONE hour,
then FOUR machines makes 4 widgets in ONE hour,
which means FOUR machines makes 8 widgets in TWO hours

Answer: A

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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by GMATGuruNY » Tue Aug 21, 2018 11:06 am
Time and rate have a RECIPROCAL RELATIONSHIP.
If Mary works TWICE as fast as John, Mary's time will be 1/2 John's time.
If Mary works THREE TIMES as fast as John, Mary's time will be 1/3 John's time
swerve wrote:One machine, working at a constant rate, can fill a production order in 8 hours. How long would it take four identical machines, working at the same constant rate, to fill the order?

A. 2 hours
B. 4 hours
C. 8 hours
D. 16 hours
E. 32 hour
Since 4 machines will work 4 times as fast as 1 machine, the time for 4 machines will be 1/4 the time for 1 machine:
(1/4)(8) = 2 hours.

The correct answer is A.
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by Scott@TargetTestPrep » Thu Aug 23, 2018 4:11 pm
swerve wrote:One machine, working at a constant rate, can fill a production order in 8 hours. How long would it take four identical machines, working at the same constant rate, to fill the order?

A. 2 hours
B. 4 hours
C. 8 hours
D. 16 hours
E. 32 hours
Since the rate of 1 machine is 1/8, the rate of 4 machines is 4/8 = 1/2.

Thus, it will take 4 machines 1/(1/2) = 2 hours to fill the order.

Answer: A

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