If 49 litres of a milk solution has 63% milk in it, then how much milk should be added to make the concentration of milk 70% in the solution?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 11liters
Let the amount of milk to be added = x
Amount of milk in 49 liters of milk = 63% of 49 = 49 × 63%
After adding x liters of milk, the concentration changes to 70%. So,
(49 + x) × 70% = 49 × 63% + x
⇒ 49 × 70% + 70% × x = 49 × 63% + x
⇒ 7% × 49 = x - 70% × x
⇒ 7% × 49 = x × (100 - 70)/100
⇒ 7 × 49 = 30x
⇒ x = 343/30 = 11liters