Problema Solution
a tank can be filled by one pipe in 12 hours, by a second pipe in 7 hours, and by a third pipe in 4 hours. If all three pipes are open, how long will it take to fill the tank?
Answer provided by our tutors
the rate of the first pipe is 1 tank is 12 hours that is 1/12 tank per hour
the rate of the second pipe is 1 tank is 7 hours that is 1/7 tank per hour
the rate of the third pipe is 1 tank is 4 hours that is 1/4 tank per hour
let x tank/hour be the rate when all three pipes are open then we can write
1/12 + 1/7 + 1/4 = 1/x
by solving we find
x = 2.1 h
x = 2 h 0.1*60 min
x = 2 h 6 min
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if all three pipes are open the tank will be filled in 2 hours and 6 minutes.