Question

Pipes A and B can fill a tank 30 and 20 hours respectively. Pipe B is opened only for half the time and both pipes are opened for the remaining time. Then tank will be full a) in 15 hours (b) in 20 hours (c) in 25 hours (d) 10 hours​

Answer 1

Answer:

a)in 15 hours

Pipe A 1 hr work=1/30

Pipe B 1 hr work=1/20

let total time required to fill the tank =xhrs

since pipe B is open for half hr so work done by pipe B in x/2 hrs =x/40hrs

and work done by pipe (A+B) in remaining x/2 hrs=x/24hrs

so total work done is =x/40+x/24

1=x/40+x/24

=>1=8x/120

=>120=8x

so x=15hrs

Step-by-step explanation:

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Answer 2

Answer:

15hours is the answer option a)