Solved UPSC CDS/OTA Question
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Q · Mixture and AlligationMedium · 45s
A vessel is full of pure milk. 20% of it is removed and replaced with water. This process is repeated 3 more times. If the final quantity of milk left is 25.6 liters, what was the initial quantity?
TopicMixture and Alligation
Question Typemultiple choice
DifficultyMedium
Marking+1 / −0.33
Test Duration30 min
Step-by-Step Solution
The complete worked solution.
Every step explained - no skipped algebra.
Let the initial quantity of milk be x liters.
Each time, 20% is removed → 80% remains.
After 4 repetitions, milk left =
x × (0.8)^4 = 25.6
Solve:
x × 0.4096 = 25.6
→ x = 25.6 / 0.4096 = 62.5
Final Answer: Option D - 80.5 liters