Question

Two taps A and B can fill up a cistern in 6 minutes and 8 minutes respectively. If they
are opened for 1 minute alternatively, beginning with A; in how much time will they
fill up the cistern.​

Answer 1

Answer:

Let the volume of cistern = LCM(6,7) = 42 litres

Tap A fills 7 litres in 1 minute.

Tap B fills 6 litres in 1 minute.

If they are opened alternately, they will fill 13 litres in 2 minutes.

This cycle will repeat [42/13] = 3 times taking 6 minutes filling 39 litres.

Remaining 3 litres will be filled by Tap A in 3/7 minutes.

Total time = 6 + 3/7 = 6 3/7 minutes

:-)