exam Maths Puzzle

There are 12 pipes attached to a tank. Some of them are fill pipes and some are drain pipes. Each of the fill pipes can fill the tank in 12 hours, while each of the drain pipes will take 24 hours to drain a full tank completely. If all the pipes are kept open when the tank was empty, it takes 2 hours for the tank to overflow. How many of these pipes are drain pipes?

A.

6

B.

11

C.

4

D.

7

Read Solution (Total 1)

let x+y=12,,,again (x/12 -y/24)*2=1 solve equation y=4
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exam Other Question

A work is done by three person A,B and C. A alone takes 10 hours to complete a single product but B and C working together takes 4 hours, for the completion of the same product. If all of them worked together and completed 14 products, then how many hours have they worked?

A.

20 hrs

B.

28 hrs

C.

40 hrs

D.

54 hrs
A bath can be filled by the cold water pipe in 10 min and by hot water pipe in 15 min (independently each). A person leaves the bathroom after turning on both pipes simultaneously and returns at the moments when the bath should be full. Finding, however, that the waste pipe has been open he now closes it. In 4 min more, bath is full. In what time would be the waste pipe empty it?

A.

9 min

B.

12 min

C.

15 min

D.

14 min