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Machine A can fill an order of widgets in a hours. Machine B

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Machine A can fill an order of widgets in a hours. Machine B [#permalink]

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New post 17 Sep 2011, 02:36
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Question Stats:

41% (01:39) correct 59% (01:01) wrong based on 321 sessions

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Machine A can fill an order of widgets in a hours. Machine B can fill the same order of widgets in b hours. Machines A and B begin to fill an order of widgets at noon, working together at their respective rates. If a and b are even integers, is Machine A's rate the same as that of Machine B?

(1) Machines A and B finish the order at exactly 4:48 p.m.
(2) (a + b)^2 = 400

OPEN DISCUSSION OF THIS QUESTION IS HERE: jane-can-paint-the-wall-in-j-hours-and-bill-can-paint-the-87131.html
[Reveal] Spoiler: OA

Last edited by Bunuel on 22 Jul 2013, 06:25, edited 2 times in total.
Edited the question.
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Re: DS Help [#permalink]

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New post 17 Sep 2011, 02:57
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nshang wrote:
Machine A can fill an order of widgets in a hours. Machine B can fill the same order of widgets in b hours.
Machines A and B begin to fill an order of widgets at noon, working together at their respective rates. If a and
b are even integers, is Machine A's rate the same as that of Machine B?
(1) Machines A and B finish the order at exactly 4:48 p.m.
(2) (a + b)2 = 400

Some help on this!




ok here is how...

A can do the work in a hours = > in 1 hr = 1/a
similarly B can do 1/b work in 1 hr

A: we are told that both together completed the work by 4:48 = 4+4/5 hrs = 25/5 hours

24/5 (1/a + 1/b) = 1

a+b / ab = 5/24

=> 24 a + 24 b = 5ab

if both rates are equal... 48a = 5 a ^2

or 5a = 48 => a = 9.6 but given in the question a and b are even integers.. so A and B DO NOT work at the same rate
A is sufficient

B: (a+b)2 = 400 => a+b = 200.....

possible cases a = 100, b = 100... a = 50, b = 150... so cannot say....

hence ans is A
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Re: Machine A can fill an order of widgets in a hours. Machine B [#permalink]

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New post 16 Jan 2013, 02:08
tough one..
can we expect such qs on gmat?
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Re: Machine A can fill an order of widgets in a hours. Machine B   [#permalink] 16 Jan 2013, 02:08
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Machine A can fill an order of widgets in a hours. Machine B

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