SOLUTION: A vat of chocolate can be filled by an Intel pipe in 12 hours. An outlet pipe can empty the vat in 15 hours. How long will it take to fill the vat if both pipes are left open?

Question 1027312: A vat of chocolate can be filled by an Intel pipe in 12 hours. An outlet pipe can empty the vat in 15 hours. How long will it take to fill the vat if both pipes are left open?

Found 2 solutions by Boreal, ikleyn:
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
every hour (1/12) is filled and (1/15) is emptied.
(x/12)-(x/15)=1
multiply everything by 60
5x-4x=60
x=60 hours
That would be filling the vat 5 times and emptying it 4 times.
Answer by ikleyn(52776) (Show Source): You can put this solution on YOUR website!
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A vat of chocolate can be filled by an Intel pipe in 12 hours. An outlet pipe can empty the vat in 15 hours. How long will it take to fill the vat if both pipes are left open?
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Many problems of this kind you can find in the lesson Using fractions to solve word problems on joint work in this site.

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