Question

pipe no 1 con fill the tank in 5 hours and pipe no 2 in 10 hours pipe no 3 con drain the water and make empty in 15/2 hours lf all three pipes are open all together then the time required for filing the tank completely would be

Answer 1

pipe number 1 one hour work =
$\frac{1}{5}$
pipe no. 2 one hour work is 1/10
pipe no. 3 one hour work is = - 2/15
thus work dine in 1 hour when all pipes are opened is
$\frac{1}{5} + \frac{1}{10} - \frac{2}{15} = \frac{6 + 3 + - 4}{30} = \frac{5}{30} = \frac{1}{6}$

thus time taken fill the tank is 6 hours