Timework4

4A barrel full of beer has 2 taps, one midway which draws a litre in 6 minutes and the other at the bottom which draws a litre in 4 minutes. The lower tap is normally used after the level of beer in the barrel is lower than midway. The capacity of the barrel is 36litres. A new assistant opens the lower tap when the barrel is full and draws out some beer. As a result the lower tap has been used 24 minutes before the usual time. For how long was the beer drawn out by the new assistant?

Option : C
Explanation :
Top tap is operational till 18 litres is drawn out.
∴ Time after which the lower tap is usually open = 18 x 6 = 108 minutes.
∴ Time after which it is open now = 108 - 24 = 84 minutes.
∴ Litres d rawn = 84/16 = 14 litres
∴ 18 - 14 = 4 litres
were drawn by the new assistant.
∴ Time = 4 x 4 = 16 minutes.

Alternatively
Upper tap was not used for 24 minutes.
∴ Litres drawn = 24/6 = 4 litres.
∴ Beer was drawn for 4x 4 = 16 minutes.

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