math problem?

Question

one pipe can drain a wastewater holding tank in 8 hours. if another pipe is used to work with the first pipe, working together they can drain the same wastewater holding tank in 5 hours. how long would it take for the second pipe to drain the wastewater holding tank by itself?
any help would be greatly appreciated. thanks

Answer 1

(1/8+1/x)5=1
(x+8)5=8x
5x+40=8x
40=3x
x=40/3=13 hours and 20 minutes for the second pipe to drain the tank.

Answer 2

Pipe 1 takes 8 hours.
In 1 hour it can empty 1/8 of the tank.

Both pipes combined take 5 hours
In 1 hour they can empty 1/5 of the tank

Pipe 2 can empty 1/5-1/8=3/40 of the tank in 1 hour

Pipe 2 requires 40/3 hours or 13 hours and 20 minutes to drain the tank by itself.

Answer 3

Make up some value for the total amount. i used 16.

pipe 1 takes 8 hours to drain 16 gallons. That is a rate of two gallons per hour.

In five hours pipe one will drain 10 gallons of wastewater. So that means that pipe two was able to drain 6 gallons in five hours. The hourly rate of drainage of pipe two is therefore 1.2 gallons per hour.

Now applying this rate to the original amount of 16 gallons. Then 20/1.2= 13.333 hours for pipe two alone to drain the same amount.

Answer 4

Set it up this way:

x/8 = work of first pipe.

x/5 = work done together

1/x = work done by second pipe alone.

x/8 + 1/x = x/5

Now, solve for x.

Guido

Answer 5

its boring