Three pipes, A, B, & C are attached to a tank. A & B can fill it in 20 & 30 minutes respectively while C can empty it in 15 minutes. If A, B & C are kept open successively for 0.5 minute each, how soon will the tank be filled?
Choose the correct choice.
A) 1 hour 30 min
B) 4 hours
C) 3 hours
D) 5 hours
E) 6 hours
in three minute 1/20+1/30-1/15=1/60 part is filled   1.5 min--------1/60 parts   x min--------- 1 part(full)   x=90 min =1 hour 30 min   1 hour 30 minNSWER:1 hour 30 min
<result>A</result>
Three pipes, A, B, & C are attached to a tank. A & B can fill it in 20 & 30 minutes respectively while C can empty it in 15 minutes. If A, B & C are kept open successively for 0.5 minute each, how soon will the tank be filled?