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Three machines, a, b, c, individually can do a certain job. What is th

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Three machines, a, b, c, individually can do a certain job. What is th [#permalink]

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Three machines, a, b, c, individually can do a certain job. What is the greatest part of that job that can be done in one hour by two of the machines working together at their respective rates?

(1) Machine a can complete the job in 5 hours.
(2) Machine b can complete the job in 7 hours.
[Reveal] Spoiler: OA

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Re: Three machines, a, b, c, individually can do a certain job. What is th [#permalink]

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New post 28 Mar 2017, 13:05
Bunuel wrote:
Three machines, a, b, c, individually can do a certain job. What is the greatest part of that job that can be done in one hour by two of the machines working together at their respective rates?

(1) Machine a can complete the job in 5 hours.
(2) Machine b can complete the job in 7 hours.


Answer E.

1) tells us about A but nothing about B & C.
2) Tells us about B but nothing about A & C.

1) & 2) Tell us about A & B but nothing about C. Since we can't assume C is either greater or less than A or B we can't answer the question.
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Re: Three machines, a, b, c, individually can do a certain job. What is th [#permalink]

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New post 08 Aug 2017, 01:34
I have a question here. So the statements individually are clearly not sufficient. But together, If we assume the number of units then we get the same ratio for the work completed. So is this assumption wrong because we are not given any detail about the total units done.Now if we assume the work to be of 35 units then a does 7 unit/hour and b does 5unit/hour , therefore the remaining 23 units is done by c. The required fraction is 23+7=30
30/37=6/7 (This ratio is a constant but we have to assume the units . )Where is my logic going wrong?? Can someone please help.

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Re: Three machines, a, b, c, individually can do a certain job. What is th   [#permalink] 08 Aug 2017, 01:34
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