math: rate problem

[andyjl]

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a 120-gallon tub has a drain which, when open, drains water at the rate of 6 gallons per minute. If the tub is empty and the drain is open, at what rate, in gallons of water per minute, must water be added to the tub so that it fills in exactly 1 hour?

how do you work this out?

answer is 8

 

[domonas]

a 120-gallon tub has a drain which, when open, drains water at the rate of 6 gallons per minute. If the tub is empty and the drain is open, at what rate, in gallons of water per minute, must water be added to the tub so that it fills in exactly 1 hour?

how do you work this out?

answer is 8

1 hour = 60 minutes
to fill a 120 gallon tank in 60 minutes, you need to put in 2 gal/min.
if it leaks out at 6 gal/min, you need 8 gal/min to fill the 120 gal tank.