There are two tanks A and B to fill up a water tank. The tank can be filled in 40 min, if both taps are on. The same tank can be filled in 60 min, if tap A alone is on. How much time will tap alone take, to fill up the same tank?

Correct Answer: 120 min

Part filled by tap A in 1 min = 160

Let tap B fills the tank in x min

Then, part filled by tap, B in 1 min = 1x

According to the question,

= 1/60 + 1/x = 1/40

= 1/x = 1/40 – 1/60

=> 1/x = 3−2/120 => 1/x = 1/120

Therefore, Tap B can fill the tank in 120 min.