Question

pipes A can fill the tank in 5 hours, pipe B in 10 hours and pipe c in 30 Hours. if all the pipes are open , in how many hours will the tank be filled ​

Answer 1

$a \: can \: fill \: tank \: in \: 1 \: hour = \frac{1}{5} \\ b \: can \: fill \: tank \: in \: hour = \frac{1}{10} \\ c \: can \: fill \: tank \: in1hour = \frac{1}{30} \\ so \: we \: will \: do \: sum \\ (a + b + c) \: in \: 1hr \\ = \frac{1}{5} + \frac{1}{10} + \frac{1}{30} \\ lcm = 30 \\ \frac{6}{30} + \frac{3}{30} + \frac{1}{30 } \: \\ = \frac{10}{30} \\ = \frac{1}{3}$

so all pipes can fill tank in 3hour