A cistern contains 100 liters of pure syrup. 10 liters of syrup are drawn out and replaced by water. Then, 10 liters of the mixture are drawn out and replaced by water again. What is the ratio of syrup to water in the final mixture?

Correct option is C

Given :

Initial syrup = 100 L (pure)

First operation: 10 L removed and replaced with water

Second operation: Again 10 L removed and replaced with water

Solution:

After first removal:

Syrup removed = 10 L

Syrup left = 90 L

After second removal:
Fraction of syrup in mixture = 90/100 = 0.9
So syrup removed in second draw = 10 $$\times 0.$$​9 = 9 L
Syrup left = 90 - 9 = 81 L

Water = 100 - 81 = 19 L

Ratio = 81 : 19