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combine rate question

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combine rate question

by alwayslulu » Fri Apr 30, 2010 8:00 pm
Todd's construction company is able to build 40 houses per year. Mike's construction company builds 80 houses per year .

how long does it take the two companies together to build 64 houses?

Thanks for your response. :)
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by beat_gmat_09 » Fri Apr 30, 2010 9:29 pm
alwayslulu wrote:Todd's construction company is able to build 40 houses per year. Mike's construction company builds 80 houses per year .

how long does it take the two companies together to build 64 houses?

Thanks for your response. :)
1/40 + 1/80 = x/64

x = 2.4
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by Testluv » Fri Apr 30, 2010 10:18 pm
Together, the companies make 40 + 80 = 120 houses in one year. Thus:

120 houses/1 year = 64 houses/x years

x = 8/15 of a year or (8/15) * 365 = 194 and 2/3 days.
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by beat_gmat_09 » Fri Apr 30, 2010 11:04 pm
Testluv wrote:Together, the companies make 40 + 80 = 120 houses in one year. Thus:

120 houses/1 year = 64 houses/x years

x = 8/15 of a year or (8/15) * 365 = 194 and 2/3 days.
Hi Testluv,

I was under an impression to solve the problem using the standard rate formulaes, after looking at your solution it seemed obvious to me, how should one differentiate between such problems weather to solve using the standard formulaes or to apply logic as you applier above.

Thanks
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