Question

A vessel contains 10 liters of mixture in which there is 10% water. To make the solution which contains 25% water, the quantity of water to be added in it is:
1. 5 liters
2. 4 liters
3. 3 liters
4. 2 liters 

Answer 1

Correct Answer - Option 4 : 2 liters 

Given:

Vessel contains 10 L mixture out of which 10% is water

Calculations:

Volume of the mixture is 10 liters, in which the quantity of water is 10%

⇒ 10 × (10/100) = 1 liters

We need 25% water in the mixture.

Here suppose you mix x litres water in 10 litre mixture.

Then the quantity of water = 1 + x litres

And the quantity of mixture = 10 + x litres.

We need 25% of water. So,

⇒ [(1 + x)/10 + x] × 100 = 25

⇒ (1 + x)/10 + x = 25/100

⇒ (1 + x)/10 + x = 1/4

⇒ 4 + 4x = 10 + x

⇒ 4x – x = 10 – 4

⇒ 3x = 6

⇒ x = 6/3

⇒ x = 2

∴ We should add 2 litres of water.