SOLUTION: A mowed 3/4 at his lawn in 5/4 hours.B who works twice as fast finished the job.how many minutes did B work?

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Question 585848: A mowed 3/4 at his lawn in 5/4 hours.B who works twice as fast finished the job.how many minutes did B work?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
If A mowed 3/4 of his lawn, there is 1/4 left
for B to mow
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If A mowed a lawn 4 times as large, it would take him
4 times longer, so
+4%2A%283%2F4%29+=+3+ lawns take him +4%2A%285%2F4%29+=+5+ hrs
1 lawn would take him 1/3 of that time, or +%281%2F3%29%2A5+=+5%2F3+ hrs
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If B works twice as fast, he can mow 1 lawn in +%281%2F2%29%2A%285%2F3%29+=+5%2F6+ hrs
But B only has to mow 1/4 of a lawn, so
B can mow it in +%281%2F4%29%2A%285%2F6%29+=+5%2F24+ hrs
+5%2F24+ hrs x +60+ min/hr = 12.5 minutes