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A bathtub can be filled by a tap in 20 min and by another tap in 60 min. Both the taps are kept open for 5 min then the 1st tap is shut off. After this how much time will it take for the bathtub to be filled completely?

A bathtub can be filled by a tap in 20 min and by another tap in 60 min. Both the taps are kept open for 5 min then the 1st tap is shut off. After this how much time will it take for the bathtub to be filled completely? Correct Answer 40 min

Given:

A bathtub can be filled by two taps in = 20 min and 60 min

Calculation:

Part of the tank filled by both in 5 min

⇒ 5 × (1/20 + 1/60)

⇒ 5 × (6 + 2)/120

⇒ 8/24

⇒ 1/3

∴ Remaining part = (1 – 1/3)

⇒ 2/3

∴ 1/60 part is filled in 1 min

∴ 2/3 part is filled in

⇒ (2/3) × 60

⇒ 40 min

It takes 40 min for the bathtub to be filled completely.

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