Solved UPSC CDS/OTA Question
A solved UPSC CDS/OTA PYQ — decoded step-by-step.
Solve it the standard way once — then learn the shortcut.
Q · Time and WorkMedium · 45s
A tank holds 100 gallons of water. Its inlet is 7 inches in diameter and fills the tank at 5 gallons/min. The outlet of the tank is twice the diameter of the inlet. How many minutes will it take to empty the tank if the inlet is shut off, when the tank is full and the outlet is opened? (Hint: Rate of filling or emptying is directly proportional to the diameter)
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.
Final Answer: Option B — 10.0 min