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# A is 30% more efficient than B. How much time will they take to

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Manager
Joined: 13 Aug 2018
Posts: 55
A is 30% more efficient than B. How much time will they take to  [#permalink]

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25 May 2019, 04:41
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Difficulty:

55% (hard)

Question Stats:

61% (02:06) correct 39% (01:57) wrong based on 62 sessions

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A is 30% more efficient than B. How much time will they take to complete a job by working together, which A alone could have done in 23 days?

A. 10 days
B. 13 days
C. 15 days
D. 17 days
E. 19 days
NUS School Moderator
Joined: 18 Jul 2018
Posts: 1027
Location: India
Concentration: Finance, Marketing
WE: Engineering (Energy and Utilities)
Re: A is 30% more efficient than B. How much time will they take to  [#permalink]

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25 May 2019, 07:30
1
A takes 23 days to finish.
As the Efficiency of B is 1.3 times of A, then B takes 1.3*23 days.

1/A+1/B = 1/X
1/23+10/13*23 = (10+13)/13*23 = 1/X

X = (13*23)/23 = 13 days.

Director
Joined: 27 May 2012
Posts: 947
Re: A is 30% more efficient than B. How much time will they take to  [#permalink]

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26 May 2019, 11:23
Chethan92 wrote:
A takes 23 days to finish.
As the Efficiency of B is 1.3 times of A, then B takes 1.3*23 days.

1/A+1/B = 1/X
1/23+10/13*23 = (10+13)/13*23 = 1/X

X = (13*23)/23 = 13 days.

Hi Chethan92,
Please note A is 30% more efficient than B and not the other way round.
Also when Something is more efficient it takes lesser time NOT more.

You have taken B to be more efficient at the same time, B is taking more time??
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- Stne
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Re: A is 30% more efficient than B. How much time will they take to  [#permalink]

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26 May 2019, 11:27
stne wrote:
Chethan92 wrote:
A takes 23 days to finish.
As the Efficiency of B is 1.3 times of A, then B takes 1.3*23 days.

1/A+1/B = 1/X
1/23+10/13*23 = (10+13)/13*23 = 1/X

X = (13*23)/23 = 13 days.

Hi Chethan92,
Please note A is 30% more efficient than B and not the other way round.
Also when Something is more efficient it takes lesser time NOT more.

You have taken B to be more efficient at the same time, B is taking more time??

Wording problem. And yes, I KNOW THAT THE PERSON WHO IS MORE EFFICIENT TAKES LESS TIME.
Director
Joined: 27 May 2012
Posts: 947
Re: A is 30% more efficient than B. How much time will they take to  [#permalink]

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26 May 2019, 11:30
Chethan92 wrote:
stne wrote:
Chethan92 wrote:
A takes 23 days to finish.
As the Efficiency of B is 1.3 times of A, then B takes 1.3*23 days.

1/A+1/B = 1/X
1/23+10/13*23 = (10+13)/13*23 = 1/X

X = (13*23)/23 = 13 days.

Hi Chethan92,
Please note A is 30% more efficient than B and not the other way round.
Also when Something is more efficient it takes lesser time NOT more.

You have taken B to be more efficient at the same time, B is taking more time??

Wording problem. And yes, I KNOW THAT THE PERSON WHO IS MORE EFFICIENT TAKES LESS TIME.

But then why is B taking more time , in your equation?
_________________
- Stne
NUS School Moderator
Joined: 18 Jul 2018
Posts: 1027
Location: India
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Re: A is 30% more efficient than B. How much time will they take to  [#permalink]

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26 May 2019, 11:32
A is more efficient. So, B has to take more time?

Posted from my mobile device
Director
Joined: 27 May 2012
Posts: 947
Re: A is 30% more efficient than B. How much time will they take to  [#permalink]

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26 May 2019, 11:35
Chethan92 wrote:
A is more efficient. So, B has to take more time?

Posted from my mobile device

I was talking about YOUR EQUATION in which you have taken B to be more efficient than A.
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- Stne
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Re: A is 30% more efficient than B. How much time will they take to  [#permalink]

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26 May 2019, 11:37
As I SAID BEFORE, I should have wrote it as time taken by B is 1.3times of A.

Posted from my mobile device
Senior Manager
Joined: 03 Mar 2017
Posts: 373
Re: A is 30% more efficient than B. How much time will they take to  [#permalink]

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27 May 2019, 18:25
Chethan92 wrote:
A takes 23 days to finish.
As the Efficiency of B is 1.3 times of A, then B takes 1.3*23 days.

1/A+1/B = 1/X
1/23+10/13*23 = (10+13)/13*23 = 1/X

X = (13*23)/23 = 13 days.

The problem with your solution is the line highlighted.

Its not B that is efficient . You should correct it and write "As the Efficiency of A is 1.3 times of B, B takes 1.3*23 days.

This will clear your and others concepts as well.

No offenses mate!!
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Re: A is 30% more efficient than B. How much time will they take to  [#permalink]

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27 May 2019, 18:33
1
jackfr2 wrote:
A is 30% more efficient than B. How much time will they take to complete a job by working together, which A alone could have done in 23 days?

A. 10 days
B. 13 days
C. 15 days
D. 17 days
E. 19 days

Let efficiency A= 130 and B=100, we have to find x
A23 = (A+B)x
130 * 23 = 230 * x
x=13 B
Re: A is 30% more efficient than B. How much time will they take to   [#permalink] 27 May 2019, 18:33
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