If Max can complete a job in 4 hours and Nick can complete

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BTGmoderatorLU: Moderator; Posts: 2505; Joined: Sun Oct 15, 2017 1:50 pm; Followed by:6 members

If Max can complete a job in 4 hours and Nick can complete

by BTGmoderatorLU » Wed Oct 03, 2018 2:38 pm

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Source: Princeton Review

If Max can complete a job in 4 hours and Nick can complete the same job in 6 hours, how many fewer hours do Max and Nick working together need to complete the job than Max alone needs to complete the job?

A. 1.6
B. 2.4
C. 3.2
D. 3.4
E. 5.0

The OA is A.

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Source: Beat The GMAT — Problem Solving | Wed Oct 03, 2018 2:38 pm

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by [email protected] » Wed Oct 03, 2018 4:22 pm

Hi All,

We're told that Max can complete a job in 4 hours and Nick can complete the same job in 6 hours. We're asked how many FEWER hours it would take Max and Nick working together to complete the job than Max alone needs to complete the job. This question can be solved in a couple of different ways, including with the Work Formula.

Work = (A)(B)/(A+B) where A and B are the two times the individuals take to complete the job alone.

With Max's time of 4 hours and Nick's time of 6 hours, working together, it would take them...

(4)(6)/(4+6) = 24/10 = 2.4 hours to complete the job

The difference between Max's time and 'combined' time is 4 - 2.4 = 1.6 hours.

Final Answer: A

GMAT assassins aren't born, they're made,
Rich

Contact Rich at [email protected]

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Scott@TargetTestPrep: GMAT Instructor; Posts: 8086; Joined: Sat Apr 25, 2015 10:56 am; Location: Los Angeles, CA; Thanked: 43 times; Followed by:29 members

by Scott@TargetTestPrep » Thu Oct 04, 2018 6:32 pm

BTGmoderatorLU wrote:Source: Princeton Review

If Max can complete a job in 4 hours and Nick can complete the same job in 6 hours, how many fewer hours do Max and Nick working together need to complete the job than Max alone needs to complete the job?

A. 1.6
B. 2.4
C. 3.2
D. 3.4
E. 5.0

The combined rate for Max and Nick is:

1/4 + 1/6 = 3/12 + 2/12 = 5/12, so the time needed to completed the job together is 12/5 = 2.4 hours.

So it takes 4 - 2.4 = 1.6 hours less when they complete the job together than if Max were to complete the job alone.

Answer: A

Scott Woodbury-Stewart
Founder and CEO
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