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M25 #16

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Intern
Joined: 25 Jun 2013
Posts: 3

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15 Jul 2013, 13:30
1
KUDOS
I'm beginning to really like these type of questions. Answer is definitely D.
Manager
Status: suffer now and live forever as a champion!!!
Joined: 01 Sep 2013
Posts: 148
Location: India
GPA: 3.5
WE: Information Technology (Computer Software)

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29 May 2014, 03:20
jack can complete the task in 8hrs. -> 1/8th of the work in 1hr;
tom can complete the task in 12 hrs -> 1/12th of the work in 1 hr;

jack alone works for 4hrs -> 1/2 of the work is done alone by the jack alone.
For remaining 1/2 of the work , jack and tom together work .

Combined rate of jack and tom is 1/8+1/2 = 5/24;

Work =rate * time ;

1/2 = 5/24 * time;

time = 24/10 = 2.4hrs;
Intern
Joined: 22 Mar 2013
Posts: 21
Concentration: Operations, Entrepreneurship
GMAT 1: 620 Q47 V28
GMAT 2: 680 Q45 V38
WE: Engineering (Manufacturing)

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19 Jun 2014, 05:53
Jack finished 1/2 of work in 4 hours at his rate (1/8). Now, 1/2 of work is left when Tom joins in. If Tom and Jack had same rate of 1/8 (i.e. they each took 8 hrs to finish the task), then they together would have finished the remaining task in 2 hours, and Jack would have worked a total of 6 hours. But, we can see that Tom's rate is less than Jacks. Therefore, they must have taken more than 2 hours to finish the remaining task. This means that Jack must have worked for more than 6 hours total. By now, options A, B, and C are cancelled out. Now, option D says that Jack worked a little above 6 hours (6 hrs meant that their rates were same) and option E says that Jack worked almost 8 hours. A closer look at their rates will suggest that if option E were correct, then Tom's rate would have been almost half of Jack's rate, which is not the case. Hence, option D is correct.
Re: M25 #16   [#permalink] 19 Jun 2014, 05:53

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M25 #16

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