Question

two pipes a and b can fill a tank in 20 minutes and 30 minutes respectively . If initially only pipe b was kept open for 2/5th of the total time and both pipes a and b were kept open for the rest of the time then how many minutes would both pipes take to fill the tank​

Answer 1

Step-by-step explanation:

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=15hrslet x will be completion time

so, x/2*(1/20) + x/2*(1/30 + 1/20)=1

8x=120

x=120/8

x=15 ans

I hope it will help you to understand ❤