Step-by-step explanation:

time taken by pipe 1= 36 min

time taken by pipe 2= 48 min

water emptied by both pipe in 1 min=1/36+1/48

l.c.m of 36 and 48=144

4+3/144=7/144

so,total time taken by is reciprocal of 7/144

=144/7

Answer:

144min

Step-by-step explanation:

in one min it fills 1/36

in one min it emptied 1/48

when both the pipes are open then it fills in one min (1 \div 36) - (1 \div 48)

=1/144

I.e . in 144min the cistern can fill