TS ICET 23 May 2018 Shift 2 Paper

Question : 96 of 200

Marks: +1, -0

Two taps A and B can independently fill a tank in 30 minutes and 45 minutes respectively and a pump C can empty full tank in 20 minutes. If all are opened for 10 minutes and the pump C is closed, then the time required to fill the tank (in minutes) is?

17
$25 1/3$
$15 1/3$
27

Validate

Solution:

Rate of filling the tank taps A, tap B and pump C are 1/30, 1/45 and -1/20 respectively
Let the total time to fill the tank be t minutes.
Since C was open only for 10 minutes,

\;{t}/{30}+{t}/{45}-{10}/{20}=1 ⇒{3 t+2 t}/{90}=1+{1}/{2}={3}/{2}

⇒ t ={3}/{2} ×{90}/{5}=27

minutes

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