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# A& B on working together take n hours to complete work.

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Manager
Joined: 18 Feb 2019
Posts: 163
Location: India
GMAT 1: 490 Q47 V13
GPA: 3.6
A& B on working together take n hours to complete work.  [#permalink]

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04 Mar 2019, 10:55
00:00

Difficulty:

45% (medium)

Question Stats:

47% (01:02) correct 53% (01:45) wrong based on 19 sessions

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A& B on working together take n hours to complete work. If B takes (n+9) hours to complete the work alone, how many hours will A take to complete the work alone?

I. A takes 5 hours less than B, to complete the work alone.
II. n=6
Director
Joined: 18 Jul 2018
Posts: 762
Location: India
Concentration: Finance, Marketing
WE: Engineering (Energy and Utilities)
Re: A& B on working together take n hours to complete work.  [#permalink]

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04 Mar 2019, 11:08
Given that $$\frac{1}{A}+\frac{1}{B} = \frac{1}{n}$$
Also, $$\frac{1}{B} = \frac{1}{n+9}$$

From S1:

A takes 5 hours less, means A takes n+4 hours.
From the given info, $$\frac{1}{n+4}+\frac{1}{n+9} = \frac{1}{n}$$
Solving gives, n = 6.
Sufficient.

From S2:

Given n = 6. then A takes n+4 = 10 hours.
Sufficient.

Similar question to practice.

https://gmatclub.com/forum/machines-a-and-b-working-together-take-t-minutes-to-comple-147714.html
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Re: A& B on working together take n hours to complete work.   [#permalink] 04 Mar 2019, 11:08
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