Question

Pipe A can fill an empty tank in $5$ hours while pipe B can empty the fill tank in $6$ hours. If both are opened at the same time in the empty tank, how much time will they take to fill it up completely?

Answer 1

Pipe $A$ can billion empty tanks in $5hrs$

$\Rightarrow$ billed by pipe $A$ in hr $=\frac{1}{5}$

Pipe $B$ can fill an empty tank in $6hrs.$

$\Rightarrow$ Part filled by pipe $B$ in $1hr=\frac{1}{6}$

$\therefore$ tank filled by pipe $AandB$ together in 1 hr $=\frac{1}{5}-\frac{1}{6}=\frac{1}{30}$

$\therefore$ the tank can be filled in $30hrs.$