Question 379509
Let x=time needed to fill tank with both pipe and hose turned on
Then, together, the pipe and hose fills at the rate of 1/x tank per min
Pipe fills at the rate of 1/5 tank per min
Hose fills at the rate of 1/8 tank per min
Together the pipe and hose fills at the rate of 1/5 + 1/8 tank per min
So our equation to solve is
1/5+1/8=1/x  multiply each term by 40x
8x+5x=40
13x=40
x=3.077 min----time needed with both pipe and hose working together

CK
in 3.077 min, pipe fills (1/5)*3.077 of the tank
In 3.077 min hose fills (1/8)*3.077 of the tank

(1/5)*3.077 +(1/8)*3.077 should equal 1 tank
24.616/40 + 15.385/40=1
40.001/40~~~~~~~1

Hope this helps--ptaylor