word problem

sop

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Aug 20, 2005
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Kerri, Ethan, and Jack assembled a very large puzzle together in 40 hours. If Ethan worked twice as fast as Jack and Kerri worked as fast as Ethan, then how long would it have taken Jack to assemble the puzzle alone?

I came up with an answer of 60. Is that correct?


Thanks for all your help,
SOP
 
sop said:
I came up with an answer of 60. Is that correct?
To determine if a solution is correct, check it.

. . . . .hours to complete:
. . . . .jack: 60
. . . . .ethan: 30
. . . . .kerri: 30
. . . . .together: 40

. . . . .completed per hour:
. . . . .jack: 1/60
. . . . .ethan: 1/30
. . . . .kerry: 1/30
. . . . .together: 1/40

. . . . .adding their labors:
. . . . .1/60 + 1/30 + 1/30 ?=? 1/40
. . . . .1/60 + 2/60 + 2/60 ?=? 1/40
. . . . .5/60 ?=? 1/40
. . . . .1/12 ?=? 1/40

Since 1/12 does not equal 1/40, your solution would not appear to be valid. (A quicker check: If Ethan or Kerry can finish in thirty hours, why would it take all three of them forty hours?)

Eliz.
 
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