Pipe A can fill \(\frac{1}{3}\) part of a tank in 3 hours and pipe B can fill \(\frac{1}{7}\) part of the tank in 3 hours. Find how much time will they take together to fill the tank completely?

6 hr 18 min

Pipe A can fill ⇒ \(\frac{1}{3}\) part in 3 hours and

Pipe A can fill the complete tank in = 3 × 3 = 9 hours

Pipe B can fill ⇒ \(\frac{1}{7}\) part in 3 hours and

Pipe B can fill the complete tank in = 7 × 3 = 21 hours

Therefore,

Now,

Time taken by both pipes together = \(\frac{63}{A+B}\) = \(\frac{63}{10}\)

They will fill it in 6hr 18 min.