Question

Pipe A can fill a cistern In 6 hours and pipe B can 1111 it in 8 hours. Both the pipes are opened and after two hours, pipe A is closed. How much time will B take to fill the remaining part of the tank?

Answer 1

Inlet pipe A's one hour's work $=\frac{1}{6}$

Inlet pipe B's one hour's work $=\frac{1}{8}$

Both inlets one hour's work $=\frac{1}{6}+\frac{1}{8}$

$=\frac{4+3}{24}=\frac{7}{24}$

Both inlets 2 hour's work $=\frac{7}{24}\times 2=\frac{7}{12}$

Remaining work $=1-\frac{7}{12}=\frac{12-7}{12}=\frac{5}{12}$

Now pipe B can fill the $\frac{5}{12}$ tank in $=\frac{5}{12}\times 8=\frac{10}{3}$ hours

$=3\frac{1}{3}$hours