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T can work alone and will finish job in 6 hours, P & J can d [#permalink]
11 Aug 2011, 07:40

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Difficulty:

45% (medium)

Question Stats:

48% (14:01) correct
52% (02:48) wrong based on 31 sessions

T can work alone and will finish job in 6 hours, P & J can do the same independently in 3 and 2 hours each. T starts working alone and after 1 hour P joins, both of them work for another 1 hour. After that J joins them and they finish the job together. What was fraction of job done by T????

Re: Work time question [#permalink]
11 Aug 2011, 08:18

1

This post received KUDOS

KunalPratap wrote:

T can work laone and finishes job in 6 hours, P & J can do the same independently in 3 and 2 hours each. P starts working and after 1 hour P joins, both of them work for another 1 hour. After that J joins them and thet finish the job together. What was freaction of job done by P????

1) 1/9 2) 1/6 3) 1/3 4) 7/18 5) 4/9

Please correct your question. Who starts and who joins?

Re: Work time question [#permalink]
14 Aug 2011, 00:57

I too got 7/18. If T works for 1 hr and complete 1/6 work then in 20 minutes (1/3 of an hour) T can finish 1/3 of job that T does in 1 hr. So it should be 1/6*1/3=1/18. So total work done by T is: 1/6+1/6+1/18=7/18.

Re: Work time question [#permalink]
31 Oct 2011, 22:01

1

This post received KUDOS

Expert's post

KunalPratap wrote:

T can work alone and will finish job in 6 hours, P & J can do the same independently in 3 and 2 hours each. T starts working alone and after 1 hour P joins, both of them work for another 1 hour. After that J joins them and they finish the job together. What was fraction of job done by T????

1) 1/9 2) 1/6 3) 1/3 4) 7/18 5) 4/9

T alone does the work in 6 hrs so rate = 1/6 work/hr For P, the rate of work = 1/3 = 2/6 work/hr For J, the rate of work = 1/2 = 3/6 work/hr In first hour, T works alone so 1/6 of the work is done. In the second hour, T and P work so 1/6 + 2/6 = 3/6 of the work is done. Now only 2/6 of the work is left. In the third hour, they all work together at rate 1 work/hr (1/6+2/6+3/6) Since only 2/6 of the work is left, time taken = 2/6 hr Now, we know that T worked for the complete 2(2/6) hrs at the rate (1/6) so work done by T = (1/6)*2(2/6) = 7/18th of the entire work.