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

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pranab223
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Audrey 4 hours to complete a certain job. Ferris can do the [#permalink] New post   06 May 2019, 08:36
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While working alone at their respective constant rates, Audrey took 4 hours to complete a certain job. Ferris can do the same job in 3 hours. 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
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B
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Carcass
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Re: Audrey 4 hours to complete a certain job. Ferris can do the [#permalink] New post   06 May 2019, 13:08
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A = half job in 2 hours.

F = the other half NOT in two hours but 1.5 hours. 90 minutes

So, usually, he took 120 minutes (2 hours) but actually, he takes 90 minutes.

120-90=30 minutes. Divided by 3 = 10 minutes each break.

B is the answer

PS: no formulas, just logic
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Re: Audrey 4 hours to complete a certain job. Ferris can do the [#permalink] New post   14 Sep 2019, 04:32
pranab01 wrote:
Carcass wrote:
A = half job in 2 hours.

F = the other half NOT in two hours but 1.5 hours. 90 minutes

So, usually, he took 120 minutes (2 hours) but actually, he takes 90 minutes.

120-90=30 minutes. Divided by 3 = 10 minutes each break.

B is the answer

PS: no formulas, just logic


I used some formula :-D . Will this work

The rate of Audrey and Ferris working together = \(\frac{7}{12}\)

They together can complete the work in = \(\frac{12}{7} = 1.71\) hours

But they completed in 2 hours. Hence there was an excess of = \({2 - 1.71} = 30\) minutes (approx)

Since Ferris took 3 breaks of equal interval, so each interval = \(\frac{30}{3} = 10\) minutes





Could we use this method?
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Re: Audrey 4 hours to complete a certain job. Ferris can do the [#permalink] New post   14 Sep 2019, 08:29
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On The GRE you can use whatever method you want to solve a problem in the most efficient way.

Just to reach the right answer in the minor time frame.

Regards
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Re: Audrey 4 hours to complete a certain job. Ferris can do the [#permalink] New post   18 Sep 2019, 05:23
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the formula gives 0.3 of an hour and not 30 min.
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Re: Audrey 4 hours to complete a certain job. Ferris can do the [#permalink] New post   25 Sep 2019, 07:40
Carcass wrote:
A = half job in 2 hours.

F = the other half NOT in two hours but 1.5 hours. 90 minutes

So, usually, he took 120 minutes (2 hours) but actually, he takes 90 minutes.

120-90=30 minutes. Divided by 3 = 10 minutes each break.

B is the answer

PS: no formulas, just logic


How'd you know that they both completed half of the job?

In this problem it works out that way but couldn't there be a scenario where two people are working on a job and one does more work than the other?
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Re: Audrey 4 hours to complete a certain job. Ferris can do the [#permalink] New post   25 Sep 2019, 09:31
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logann2 wrote:

How'd you know that they both completed half of the job?

In this problem it works out that way but couldn't there be a scenario where two people are working on a job and one does more work than the other?


Because

In 2 hours Audrey completed \(\frac{2}{4}=\frac{1}{2}\) of the job,

and the remaining job is done by Ferris
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Re: Audrey 4 hours to complete a certain job. Ferris can do the [#permalink] New post   25 Sep 2019, 09:33
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san9090 wrote:
pranab01 wrote:
Carcass wrote:
A = half job in 2 hours.

F = the other half NOT in two hours but 1.5 hours. 90 minutes

So, usually, he took 120 minutes (2 hours) but actually, he takes 90 minutes.

120-90=30 minutes. Divided by 3 = 10 minutes each break.

B is the answer

PS: no formulas, just logic


I used some formula :-D . Will this work

The rate of Audrey and Ferris working together = \(\frac{7}{12}\)

They together can complete the work in = \(\frac{12}{7} = 1.71\) hours

But they completed in 2 hours. Hence there was an excess of = \({2 - 1.71} = 30\) minutes (approx)

Since Ferris took 3 breaks of equal interval, so each interval = \(\frac{30}{3} = 10\) minutes





Could we use this method?


No, don't use this method. This is wrong .Please refer to the explanation provided by @Carcass
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Re: Audrey 4 hours to complete a certain job. Ferris can do the [#permalink] New post   28 Sep 2019, 06:51
Carcass wrote:
A = half job in 2 hours.

F = the other half NOT in two hours but 1.5 hours. 90 minutes

So, usually, he took 120 minutes (2 hours) but actually, he takes 90 minutes.

120-90=30 minutes. Divided by 3 = 10 minutes each break.

B is the answer

PS: no formulas, just logic


can you please explain in a more simpler way? I'm not able to understand it. Please !!!
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Re: Audrey 4 hours to complete a certain job. Ferris can do the [#permalink] New post   28 Sep 2019, 10:18
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rohanpatel98 wrote:
Carcass wrote:
A = half job in 2 hours.

F = the other half NOT in two hours but 1.5 hours. 90 minutes

So, usually, he took 120 minutes (2 hours) but actually, he takes 90 minutes.

120-90=30 minutes. Divided by 3 = 10 minutes each break.

B is the answer

PS: no formulas, just logic


can you please explain in a more simpler way? I'm not able to understand it. Please !!!


It's very simple,

It says " Audrey took 4 hours to complete a certain job" but the job is completed in "2 hours"

Hence, at this rate Audrey can complete \(\frac{1}{2}\) of the work.

Next half has to be completed by Ferris and the ques says : " Ferris can do the same job in 3 hours"

meaning the remaining half of the job can be completed by Ferris in 1.5 hours or 1 hour and 30 mins or 90 mins,

BUT, he takes 120 mins (that includes the break) i.e 120 -90 = 30 mins of break , which is 10 min of each for 3 times
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Re: Audrey 4 hours to complete a certain job. Ferris can do the [#permalink] New post   07 Oct 2019, 08:32
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pranab01 wrote:
While working alone at their respective constant rates, Audrey took 4 hours to complete a certain job. Ferris can do the same job in 3 hours. 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.

Answer: B

Cheers,
Brent
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giulio
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Audrey 4 hours to complete a certain job. Ferris can do the [#permalink] New post   27 Mar 2021, 08:01
1
Why is this method wrong? I dont understand
pranab223 wrote:
san9090 wrote:
pranab01 wrote:
A = half job in 2 hours.

F = the other half NOT in two hours but 1.5 hours. 90 minutes

So, usually, he took 120 minutes (2 hours) but actually, he takes 90 minutes.

120-90=30 minutes. Divided by 3 = 10 minutes each break.

B is the answer

PS: no formulas, just logic


I used some formula :-D . Will this work

The rate of Audrey and Ferris working together = \(\frac{7}{12}\)

They together can complete the work in = \(\frac{12}{7} = 1.71\) hours

But they completed in 2 hours. Hence there was an excess of = \({2 - 1.71} = 30\) minutes (approx)

Since Ferris took 3 breaks of equal interval, so each interval = \(\frac{30}{3} = 10\) minutes





Could we use this method?


No, don't use this method. This is wrong .Please refer to the explanation provided by Carcass
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Re: Audrey 4 hours to complete a certain job. Ferris can do the [#permalink] New post   28 Sep 2022, 20:20
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