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?

A) 64 min

B) 80 min

C) 96 min

D) 120 min

Correct answer:
D) 120 min

Description for Correct answer:

Part filled by tap A in 1 min = \( \Large \frac{1}{60} \)

Let tap B fills the tank in x min

Then, part filled by tap, B in 1 min = \( \Large \frac{1}{x} \)

According to the question,

= \( \Large \frac{1}{60} \) + \( \Large \frac{1}{x} \) = \( \Large \frac{1}{40} \)

= \( \Large \frac{1}{x} \) = \( \Large \frac{1}{40} \) - \( \Large \frac{1}{60} \)

=> \( \Large \frac{1}{x} \) = \( \Large \frac{3-2}{120} \) => \( \Large \frac{1}{x} \) = \( \Large \frac{1}{120} \)

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



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