ank can be filled in 7 hours​ (using the​ in-valve). Using the​ out-valve, the tank can be emptied in 14 hours.how long will it take to fill the​ tank?

Question

At a dairy plant, a milk tank can be filled in 7 hours (using the in-valve). Using the out-valve, the tank can be emptied in 14 hours. If both valves are open and milk is being pumped into the tank, how long will it take to fill the tank?

Answer 1

in valve fills 1/7 of the tank per hour

 

out value empties 1/14 of the tank per hour

 

1/7 - 1/14 = 2/14 - 1/14 = 1/14

 

So when they are both open 1/14 of the tank fills per hour

So 14 hours