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# If it takes Daniel 9 hours to clean an office building and it takes Ma

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Math Expert
Joined: 02 Sep 2009
Posts: 51215
If it takes Daniel 9 hours to clean an office building and it takes Ma  [#permalink]

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22 Nov 2018, 00:12
00:00

Difficulty:

15% (low)

Question Stats:

88% (01:02) correct 12% (01:01) wrong based on 25 sessions

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If it takes Daniel 9 hours to clean an office building and it takes Mark 6 hours, how long would it take the two of them, working together, to clean the building?

A. 3 hours
B. 3 hours 36 minutes
C. 4 hours 45 minutes
D. 6 hours
E. 7 hours 30 minutes

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Manager
Joined: 13 Jan 2018
Posts: 128
Location: India
GMAT 1: 580 Q47 V23
GPA: 4
If it takes Daniel 9 hours to clean an office building and it takes Ma  [#permalink]

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22 Nov 2018, 00:36
Work done by Daniel in 1 hour = $$\frac{1}{9}$$

Work done by Mark in 1 hour = $$\frac{1}{6}$$

Together work done = $$\frac{1}{9}$$ + $$\frac{1}{6}$$

= $$\frac{5}{18}$$

This is work done in 1 hour. So they can complete the work in $$\frac{18}{5}$$ hours or 216 minutes or 3 hours 36 minutes.

OPTION: B
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Director
Joined: 18 Aug 2017
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Location: India
Concentration: Sustainability, Marketing
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Re: If it takes Daniel 9 hours to clean an office building and it takes Ma  [#permalink]

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22 Nov 2018, 00:47
Bunuel wrote:
If it takes Daniel 9 hours to clean an office building and it takes Mark 6 hours, how long would it take the two of them, working together, to clean the building?

A. 3 hours
B. 3 hours 36 minutes
C. 4 hours 45 minutes
D. 6 hours
E. 7 hours 30 minutes

combined hours :1/9+1/6
= 54/15
or 54*60/15= 216 minutes or 180 + 36 mins or 3 hrs and 36 mins option B
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SVP
Joined: 26 Mar 2013
Posts: 1911
Re: If it takes Daniel 9 hours to clean an office building and it takes Ma  [#permalink]

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23 Nov 2018, 03:44
Bunuel wrote:
If it takes Daniel 9 hours to clean an office building and it takes Mark 6 hours, how long would it take the two of them, working together, to clean the building?

A. 3 hours
B. 3 hours 36 minutes
C. 4 hours 45 minutes
D. 6 hours
E. 7 hours 30 minutes

Total time = (A)(B)/(A+B)......where A & B are times.

Total time = 54/15 =3.something........only one answer fits

Re: If it takes Daniel 9 hours to clean an office building and it takes Ma &nbs [#permalink] 23 Nov 2018, 03:44
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