A cistern contains 120 liters of pure syrup. 12 liters of syrup are drawn out and replaced by water. Then, 12 liters of the mixture are drawn out and replaced by water again. What is the ratio of syrup to water in the final mixture?
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Correct answer: C
Explanation
The correct answer is option 3 i.e. 81 : 19.
Formula for remqaining syrup = Initial syrup × (1 - Syrup drawn/Initial syrup)n
⇒ Remaining syrup = 120(1 - 12/120)2
⇒ Remaining syrup = 120 × 81/100
⇒ Remaining syrup = 97.2
Amount of water added = 120 - 97.2 = 22.8
Ratio of syrup to water = 97.2 : 22.8
⇒ 972 : 228 = 81 : 19