One pipe can fill a tank in 12 hours and another can fill the tank in 8 hours. How long would it take to fill the tank using both of the pipes

It will take 4 hours and 48 minutes with both pipes.

Step-by-step explanation:

Add their rates of filling

1st pipe's rate = (1 tank) / (12 hrs)

2nd pipe's rate = (1 tank) / (8 hrs)

Let, t = hrs to fill tank using both pipes

(1 / 12) + (1 / 8) = (1 / t)

Multiply both sides by 24t

2t + 3t = 24

5t = 24

t = 4.8

0.8 x 60 = 48

It will take 4 hours and 48 minutes with both pipes