You can put this solution on YOUR website!
YOU ARE CORRECT!!! THE ANSWER IS SIX HOURS.
Let t=time required for Pipe C to empty the tank
Pipe C empties the tank at the rate of 1/t tank per hour
Pipe A fills at the rate of 1/2 tank per hour
Pipe B fills tha tank in t/2 hours, so
Pipe B fills at the rate of 2/t tank per hour
When all three pipes are open they fill at the rate of 1/1.5 tank per hour. So our equation to solve is:
1/2+1/t=1/1.5 multiply each term by 6t
3t+6=4t subtract 3t from each side
3t-3t+6=4t-3t collect like terms
t=6 hours------------------time required for Pipe C to empty the tank
Hope this helps---ptaylor