Solved UPSC CDS/OTA Question
A solved UPSC CDS/OTA PYQ — decoded step-by-step.
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Q · Time and WorkMedium · 45s
A tap can fill a tank in 12 hours, while a leak at the bottom can empty it in 18 hours. If both are open together when the tank is empty, how long will it take to fill the tank?
TopicTime and Work
Question Typemultiple choice
DifficultyMedium
Marking+1 / −0.25
Test Duration30 min
Step-by-Step Solution
The complete worked solution.
Every step explained — no skipped algebra.
Net rate = (1/12 - 1/18) = 1/36 tank/hour. Time to fill = 1 ÷ (1/36) = 36 hours.
Final Answer: Option D — 72/5 hours