A cistern has two taps one at the top and the other at the bottom . the top tap fills the cistern in one hour and the bottom tap empties the cistern in 1.5hours . if both the taps kept open at the same time, in how many hours the cistern will be filled in fully?

Asked by sowmya subathra | 19th Apr, 2013, 07:22: AM

Expert Answer:

Let the volume of the cistern be V
Rate of filling the cistern by top tap = V/1
Rate of emptying the cistern by bottom tap = V/1.5
 
Let after t hours the cistern be full
 
Hence (V/1-V/1.5) *t = V
 
0.5V/1.5V *t = V
t = 3 hours

Answered by  | 19th Apr, 2013, 08:02: AM

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