BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

Combine work

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Newbie | Next Rank: 10 Posts
Posts: 4
Joined: Sun Nov 09, 2008 9:59 pm

Combine work

by ABADONNA » Wed Jul 01, 2009 2:34 am
John can complete a task in 6 hours. Two hours after he started working, another boy, Jim, joined him and the guys completed the task together, working another 3 hours. If Jim worked alone, how long would he take to complete task?

8 hours
10 hours
12 hours
15 hours
18 hours
Top
Source: — Problem Solving |
Master | Next Rank: 500 Posts
Posts: 199
Joined: Mon Apr 06, 2009 4:15 am
Location: India
Thanked: 13 times

by gauravgundal » Wed Jul 01, 2009 2:46 am
IMO 18 hours
Let me know if i am right , i will let you know how i have done
Top
Newbie | Next Rank: 10 Posts
Posts: 4
Joined: Sun Nov 09, 2008 9:59 pm

by ABADONNA » Wed Jul 01, 2009 2:52 am
Actually I only have an answers and dont know the right answer. )
Top
Legendary Member
Posts: 752
Joined: Sun May 17, 2009 11:04 pm
Location: Tokyo
Thanked: 81 times
GMAT Score:680

by tohellandback » Wed Jul 01, 2009 3:31 am
IMO 18 hours.
you can always solve it by algebra but I love to do reasoning.
so together they finish in 5 hours.
if john had worked alone he would have finished in 6 hours.
so Jim did in 3 hours what john does in an hour
in one hour john does 1/6 of work.
so to finish the work john will take 3*6 hours(coz 6*1/6=1)
The powers of two are bloody impolite!!
Top
Master | Next Rank: 500 Posts
Posts: 392
Joined: Thu Jan 15, 2009 12:52 pm
Location: New Jersey
Thanked: 76 times

by truplayer256 » Wed Jul 01, 2009 6:59 am
Yeah, 18 hours is what I got too.

Alright, so John takes 6 hours to complete a task and 2 hours after he started, his friend, Jim comes along and begins to help him. Working together, they finish the remaining task in 3 hours.

So, John has already finished 2/6 or 1/3 of the task, so it'll take him 4 hours to finish the remaining 2/3 of the task.

1/4+1/Jim=1/3

Jim= The number of hours it'll take Jim alone to complete 2/3 of the task.

1/3-1/4=1/Jim

1/12=1/Jim

Jim=12 hours to finish 2/3 of the task

It'll take Jim 6*3 or 18 hours to finish the whole task working alone.
Top
Post new topic Post Reply
• Page 1 of 1