Question 76963
Let x=number of hours that it takes both pumps to unload all the tanker

Pump A unloads at the rate of 1/15th tanker per hour

Pump B unloads at the rate of 1/25th tanker per hour

Pump A + Pump B together unloads at the rate of 1/15+1/25 tanker per hour:

1/15=5/75
1/25=3/75

5/75+3/75=8/75 tanker per hour

So, Pump A + Pump B together unloads at the rate of 8/75 tanker per hour


Now we know that the rate that both unload times number of hours to unload the whole thing equals the whole thing off loaded.  So our equation to solve is:


(8/75)x=75/75  (Note: 75/75 denotes all the tankers load)

multiply both sides by 75  and we get

8x=75
x=9.375 hours-9h 22.5m

And 2:30 am plus 9h 22.5m=11:52.5 AM------------------answer




Hope this helps----ptaylor