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# Audrey 4 hours to complete a certain job. Ferris can do the

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Intern
Joined: 04 Feb 2018
Posts: 44
Re: Audrey 4 hours to complete a certain job. Ferris can do the  [#permalink]

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06 Aug 2019, 15:42
Let total work be equal to 12 units
Efficiency of Audrey = 3 units per hour
Efficiency of Ferris = 4 units per hour
At his current work rate, Ferris was required to complete 8 units of the task in the two hours that they both spent on the task.
Similarly, Audrey is expected to complete 6 units of the task during the 2-hour duration.
Since Audrey actually spent all the 2 hours on the task, it implies that he actually completed 6 units. This implies that the remaining 6 units were completed by Ferris. It further implies that Ferris did only 6 units instead of the 8 required. Therefore the time spent on breaks is equivalent to the time required to complete 2 units.
Ferris' efficiency indicates that he is capable of completing 4 units of work in 1 hours.
Therefore, he should be able to complete 2 units of work in 30 minutes. This implies that his total break time was 30 minutes. Since he took 3 breaks, the duration of each of his breaks was 10 minutes (30/3).
Therefore the correct answer is B.
Intern
Joined: 25 Nov 2015
Posts: 5
Location: Brazil
Concentration: General Management, Operations
Schools: IESE '21
WE: General Management (Consumer Products)
Re: Audrey 4 hours to complete a certain job. Ferris can do the  [#permalink]

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08 Aug 2019, 15:50
After working for 4 hours, Audrey completed 1/2 of the total (2h * 1/4).

So the ammount of work that remained to Ferris was 1/2.

If Ferris needs 180 min to complete the work, to complete a half of the work he needs 90 minutes.

So, the remaining 30 minutes are equivalent to three breakes of 10 minutes.
GMAT Club Legend
Joined: 12 Sep 2015
Posts: 4132
Re: Audrey 4 hours to complete a certain job. Ferris can do the  [#permalink]

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20 Oct 2019, 07:02
Top Contributor
gary391 wrote:
Audrey 4 hours to complete a certain job. Ferris can do the same job in 3hours. Audrey and Ferris decided to collaborate on the job, working at their respective rates. While Audrey worked continuously, Ferris took 3 breaks of equal length. If the two completed the job together in 2 hours, how many minutes long was each of Ferris’ breaks ?

A. 5
B. 10
C. 15
D. 20
E. 25

Audrey can complete a certain job in 4 hours, while Ferris can do the same job in 3 hours.
So, Audrey's RATE = 1/4 of the job per hour
And Ferris' RATE = 1/3 of the job per hour

Audrey and Ferris worked together on the job and completed it in 2 hours, but while Audrey worked this entire time, Ferris worked for some of the time and took 3 breaks of equal length.
Since Audrey works for the entire 2 hours, let's determine how much work she does.
At a rate of 1/4 of the job per hour, Audrey can complete 1/2 of the job in TWO hours.

This means Ferris must have completed the other 1/2 of the job

Time = output/rate
So, Ferris' work time = (1/2)/(1/3) = 3/2 hours = 90 MINUTES

So, at his normal rate of work, Ferris can complete his half of the job in 90 MINUTES, which meanshe rested for the other 30 minutes.

How many minutes long was each of Ferris's break?
Ferris took 3 breaks of equal length
If he rested for a TOTAL of 30 minutes, each break was 10 minutes long.

Cheers,
Brent
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Re: Audrey 4 hours to complete a certain job. Ferris can do the   [#permalink] 20 Oct 2019, 07:02

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