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Jane and Ashley take 20 days and 40 days respectively to [#permalink]
27 Dec 2012, 13:36

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Question Stats:

56% (03:15) correct
44% (02:39) wrong based on 163 sessions

Jane and Ashley take 20 days and 40 days respectively to complete a project when they work on it alone. They thought if they worked on the project together, they would take fewer days to complete it. During the period that they were working together, Jane took an eight day leave from work. This led to Jane's working for four extra days on her own to complete the project. How long did it take to finish the project ?

(A) 10 Days (B) 15 Days (C) 16 Days (D) 18 Days (E) 20 Days

Re: Jane and Ashley take 20 days and 40 days respectively to [#permalink]
27 Dec 2012, 14:57

tabsang wrote:

Jane and Ashley take 20 days and 40 days respectively to complete a project when they work on it alone. They thought if they worked on the project together, they would take fewer days to complete it. During the period that they were working together, Jane took an eight day leave from work. This led to Jane's working for four extra days on her own to complete the project. How long did it take to finish the project ?

(A) 10 Days (B) 15 Days (C) 16 Days (D) 18 Days (E) 20 Days

Assume Jane and Ashley worked together for x days without considering the 8 day leave of Jane. They would have completed \(x(\frac{1}{40} + \frac{1}{20})\) of the total work in those days. In the period when Jane took a 8 day leave, Ashley worked alone. So Ashley worked alone for 8 days. He would have completed \(\frac{8}{40}\) th of the total work. The work finished before Jane started working alone, is \(x(\frac{1}{20} + \frac{1}{40}) + \frac{8}{40}\). This is equal to \(\frac{4}{5}\) of the total work as in the period when Jane was working alone which is 4 days, she would have completed \(\frac{4}{20}\) or \(\frac{1}{5}\) of the work. Previously done work is therefore \(\frac{4}{5}\).

Re: Jane and Ashley take 20 days and 40 days respectively to [#permalink]
27 Dec 2012, 16:06

I generally use take a constant (LCM) and a production example for this kind of questions.

Assuming that Jane and Ashley's work is production of certain number of Toys

In 20 days Jane completes making certain number of Toys and the same number of Toys takes 40 days for Ashley to complete, so we take the LCM (Lowest common Multiple) which would be the target work = 80 toys to complete

From above assumption we know that Jane completes 4 toys / day as in 80/20 days

And Ashley completes 2 toys / Day as in 80/40 days

Now if both worked without any break they would take 80/4+2 days to complete which is 13.333 days, so that eliminates choice (A) = 10 days

Now plugging in choices, B - Jane completes (15-8)*4 = 28 Ashley completes 15*2 =30 Total work in 15 days with 8 days break by Jane = 28+30 = 58 toys Jane works for 4 days on her own = 4*4 = 16 toys So in 15 days ( both Jane & Ashley)+ 4 days(only Jane) they complete 58+16 =74 toys, 6 short of the target of 80

Plug in choice C - Ashley completes 16*2= 32 toys Jane completes 8*4 = 32 toys Total in 16 days = 64 toys Jane takes 4 days on her own, 4*4 = 16 toys So in 16 days ( both Jane & Ashley)+ 4 days(only Jane) they complete = 64+16 = 80 toys which is the target.

Re: Jane and Ashley take 20 days and 40 days respectively to [#permalink]
31 Jan 2013, 19:47

SravnaTestPrep wrote:

tabsang wrote:

Jane and Ashley take 20 days and 40 days respectively to complete a project when they work on it alone. They thought if they worked on the project together, they would take fewer days to complete it. During the period that they were working together, Jane took an eight day leave from work. This led to Jane's working for four extra days on her own to complete the project. How long did it take to finish the project ?

(A) 10 Days (B) 15 Days (C) 16 Days (D) 18 Days (E) 20 Days

Assume Jane and Ashley worked together for x days without considering the 8 day leave of Jane. They would have completed \(x(\frac{1}{40} + \frac{1}{20})\) of the total work in those days. In the period when Jane took a 8 day leave, Ashley worked alone. So Ashley worked alone for 8 days. He would have completed \(\frac{8}{40}\) th of the total work. The work finished before Jane started working alone, is \(x(\frac{1}{20} + \frac{1}{40}) + \frac{8}{40}\). This is equal to \(\frac{4}{5}\) of the total work as in the period when Jane was working alone which is 4 days, she would have completed \(\frac{4}{20}\) or \(\frac{1}{5}\) of the work. Previously done work is therefore \(\frac{4}{5}\).

Re: Jane and Ashley take 20 days and 40 days respectively to [#permalink]
31 Jan 2013, 20:39

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tabsang wrote:

Jane and Ashley take 20 days and 40 days respectively to complete a project when they work on it alone. They thought if they worked on the project together, they would take fewer days to complete it. During the period that they were working together, Jane took an eight day leave from work. This led to Jane's working for four extra days on her own to complete the project. How long did it take to finish the project ?

(A) 10 Days (B) 15 Days (C) 16 Days (D) 18 Days (E) 20 Days

Remember, Work = Rate*Time and Rate = 1/Time

Ashley worked alone on the project for 8 days. Work done in these 8 days = R*T = (1/40)*8 = 1/5 Jane worked alone on the project for 4 days. Work done in these 4 days = R*T = (1/20)*4 = 1/5 Leftover work = 1 - 1/5 - 1/5 = 3/5

On this 3/5 work, both worked together. Their combined rate = 1/20 + 1/40 = 3/40 3/5 = 3/40*T T = 8 days

Total time taken = 8 (Ashley worked alone) + 4(Jane worked alone) + 8 (Both worked together) = 20 days _________________

Re: Jane and Ashley take 20 days and 40 days respectively to [#permalink]
06 Apr 2014, 23:02

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Re: Jane and Ashley take 20 days and 40 days respectively to [#permalink]
21 Apr 2015, 10:04

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