8 liters Cold drink was added to a 20 liters mixture of water and alcohol such that the ratio of alcohol to that of cold drink and water is 1 : 3. Find the amount of alcohol in the solution.

Question: 8 liters Cold drink was added to a 20 liters mixture of water and alcohol such that the ratio of alcohol to that of cold drink and water is 1 : 3. Find the amount of alcohol in the solution.

Solution:
Let,
Quantity of alcohol A
Quantity of water W
Quantity of cold drinks C = 8 liters

We have a 20 liters mixture of alcohol and water.
⇒ A + W = 20
∴ W = 20 - A ................(1)

ATQ,
A : (W + C) = 1 : 3
⇒ A/(W + 8) = 1/3
⇒ 3A = W + 8
⇒ W = 3A - 8 ................(2)

From (1) and (2)
3A - 8 = 20 - A
⇒ 4A = 28
⇒ A = 7

∴ 7 liters of alcohol is present in the mixture.