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Intern
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Machine A and B are used to produce 660 cars. It takes [#permalink]
 09 Jun 2007, 18:59
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Machine A and B are used to produce 660 cars. It takes machine A 10 hours longer to produce 660 cars then machine B. Machine B produces %10 more cars per hour then machine A. how many cars an hour does machine A produce?
6
6.6
60
100
110
Can someone please explain the non-plug in way to do this...
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CEO
Joined: 17 May 2007
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Lets say machine A takes x hours to produce 660 cars
Its rate is 660/x cars in 1 hour
Machine B's rate is 660/x-10 per hour (since it takes 10 hours less than x)
according to the question B produces 10% more cars
so
600/x * 110/100 = 660/x-10
Solving this gives us 110 hours. But the question is how many cars per hour does machine one take = 660/110 = 6 hours
Answer is A.
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GMAT Club Legend
Joined: 10 Apr 2007
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Write it out in equation form. T=time R=rate of building cars
Machine A: (T+10)R=660
Machine B: T(1.1R)=660
So (T+10)R=1.1TR
Divide both sides by R to eliminate it
T+10=1.1T
10=.1T
T=100
Plug that into (T+10)R=660 for machine A
R=6 cars per hour
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