Question

A mixture of 100 liters of salt and water contains 20% salt . How much more water should be added so that water becomes 90% of the new mixture?

1. 80 liters
2. 90 liters
3. 100 liters
4. 120 liters

Answer 1

Correct Answer - Option 3 : 100 liters

Given

A mixture of 100 liters of salt and water contains 20% salt 

Water becomes 90% of the new mixture

Concept used 

Mixture and allegation concept used

Calculation

Quantity of salt in the mixture initially be 100 × 20/100 = 20 liters

⇒ Quantity of water = 100 - 20 = 80 liters

⇒ New mixture  = 1 : 9

⇒ Let the water be added x liter to make 90%

⇒  20/(80 + x) = 1/9

⇒ 80 + x = 180

⇒ x = 100 

∴ 100 litre more water should be added