Question

The ratio of milk and water in a 45 litres mixture is 3 : 2. How much water should be added to that mixture so that the ratio of milk and water becomes 9 : 11?
1. 17 litres
2. 20 litres
3. 15 litres 
4. 10 litres

Answer 1

Correct Answer - Option 3 : 15 litres 

Given:

Inital ratio = 3 ∶ 2

Total quantity = 45 litres

New ratio = 9 ∶ 11

Calculation:

Let the actual quantity of milk and water be 3x and 2x in the mixture.

So, 3x + 2x = 5x = 45 litres

Or, x = 9 litres

Actual quantity of water = 2x = 18 litres

So, the actual quantity of milk = 3x = 27 litres

In the second step, only water is added, which means, the quantity of milk remains the same.

So, 9 units of milk in second ratio = 27 litres

Then, 1 unit = 27/9 = 3 litres

Then, quantity of water from second ratio = 11 units = 33 litres

So, amount of water added = 33 litres ​- 18 litres = 15 litres