Half litre of a solution contains 15% of alcohol. To change the alcohol concentration to 50%, find the quantity of alcohol to be mixed.
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. 350 ml.
Half a liter of solution contains 15% alcohol.
So, the amount of alcohol = 500 × (15/100) = 75 ml
Let the amount of alcohol added = x ml
New volume of the solution = (500 + x) ml
New amount of alcohol = (75 + x) ml
Now, (75 + x)/(500 + x) = 50/100 = 0.5
⇒ 75 + x = 0.5(500 + x)
⇒ 75 + x = 250 + 0.5x
⇒ 0.5x = 175
⇒ x = 175/0.5 = 350
Therefore, 350 ml of alcohol needs to be mixed.