Question

10
A pipe can fill a tank in 20 min and another pipe can fill
a tank in 30 min. pipe A is open for half of the time and
A and B are opened for the other half. How long will it
take to fill the tank ?​

Answer 1

Answer:

A pipe can fill a tank in 20 min and another pipe can fill a tank in 30 min. Pipe A is opened for half of the taime and pipe A and B are opened for the other half. How long will it take to fill the tank?

In 1min pipe A can fill 1/20 of the tank

In 1min pipe B can fill 1/30 of the tank

In 1min pipe A and B together can fill 1/20+1/30=1/12 of the tank

Say pipeA only opened for x mins and pipes A and B together opened for x mins

Then portion of tank filled

= x/20+x/12 = 1

or (3x+5x)/60=1

or 8x/60=1

or 2x=15

So time taken to fill the tank = 2x=15minutes