PYQ · UPSC Combined Defence Services 2023 · Elementary Mathematics · Q35 Difficulty 2/5
Time, Work, Speed & Distance› Time & Work, Pipes & Cisterns
Three taps A, B and C together can fill a tank in 6 hours. Tap C alone can fill the tank in 12 hours. To fill the tank, when it is empty, all the three taps are started together. After working t hours, tap C is closed and the tank is filled in 8 more hours. What is t equal to ?
Answer b.
Explanation Answer · b
The initial one-third of the tank takes all three taps 2 hours. All three taps fill 1/6 tank per hour and C fills 1/12, so A+B fill 1/12. Eight hours after C closes supplies 8/12=2/3 tank; the initial 1/3 tank takes (1/3)/(1/6)=2 hours.
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