If two pipes function together, the tank will be filled in 12 h. One pipe fills the tank in 10 h faster than the other. How many hours does the faster pipe take to fill up the tank?

Correct Answer: 20 h

Let one pipe takes m h to fill the tank.

Then, the other pipe takes (m−10)h

According to the question,

Therefore, 1/m+1/(m−10)=1/12

=> m−10+m/m(m−10)=1/12

=> 12(m−10+m)=m(m−10)

=> m2−34m+120=0

=> m2−30m−4m+120=0

=> (m−30)(m−4)=0

m = 30 or 4

Faster pipe will take (30−10)h = 20 h to fill the tank.