Question 1010820
Pump A and Pump B each can empty a tank in 2hrs. Another Pump C can empty the same tank using double the time of Pump A. If all 3 pumps are working together at the same time, how long will it take to empty the tank? 
Please have a clear explanation! Thanks.

Pump A can empty the tank in 2-hrs
Its work rate=1/2
Pump B can empty the tank in 2-hrs
Its work rate=1/
Pump C can empty the tank in 4-hrs
Its work rate=1/4
sum of indv. work rates =work rate working togethe
rworking together the 3 pumps can empty the tank in x hrs
their work rate =1/x
1/2+1/2+1/4=/1/x
5/4=1/x
x=4/5
 long will it take to empty the tank? 4/5 hr