Question

6 pipes fill a tank in 120 minutes then 5 pipes will fill it in

Answer 1

time taken for a single pipe is =120/6=20
then for 5 pipes=20×5=100min

Answer 2

When 6 pipes fit a tank in 120 minutes
then 5 pipes will fit a tank in 100 minutes
=) (120×5)/6= 100 minutes