Pipe & Cisterns
Fast trick to solve the pipe and cisterns.
If two pipe 'A' and 'B' operate both at the same time that can fill a tank in 4 hr. A water pipe 'A' fill the tank '4 hr' faster than the pipe 'B' how many hr does it take the pipe 'A' to fill the tank.
STEP 1 :
Let the tank can be filled by pipe 'A' in x hr
than pipe 'B' in 'x + 4 hr'
so in 1hr tank filled by A = 1/x
and in 1hr tank filled by B = 1/(x + 4)
STEP 2 :