Solved UPSC CDS/OTA Question
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Q · Mixture and AlligationMedium · 45s
A vessel contains 80 liters of a mixture of acid and water in the ratio 7:1. How much water must be added to make the ratio 3:1?
TopicMixture and Alligation
Question Typemultiple choice
DifficultyMedium
Marking+1 / −0.33
Test Duration30 min
← Previous questionQ 54 / 54
Step-by-Step Solution
The complete worked solution.
Every step explained - no skipped algebra.
Initial mixture: 80 liters with acid : water = 7 : 1
→ Acid = (7/8) × 80 = 70 liters
→ Water = 10 liters
Let x liters of water be added.
New water = 10 + x
New total = 80 + x
New ratio:
70 / (10 + x) = 3 / 1
→ 70 = 3(10 + x)
→ 70 = 30 + 3x
→ 3x = 40
→ x = 13.33
Answer: Add 13.33 liters of water.
Final Answer: Option B - 13.33 liters