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 has an inlet pipe that can fill it in 4 hours and an outlet pipe that can empty it in 6 hours. If both are opened together, how long will it take to fill the empty 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 = 1/4 - 1/6 = (3-2)/12 = 1/12 → Time = 12 hours.
Final Answer: Option C - 12 hours