Half litre of a solution contains 15% of alcohol. To change the alcohol concentration to 50%, find the quantity of alcohol to be mixed.

Question

Accepted Answer

Step 1: Calculate the amount of alcohol in the original solution.
- Total solution = 0.5 litre = 500 ml
- Alcohol percentage = 15%
- Alcohol amount = 15% of 500 ml = (15/100) * 500 = 75 ml

Step 2: Let the quantity of pure alcohol to be added be x ml.

Step 3: After adding x ml of pure alcohol, total alcohol = 75 + x ml
Total solution volume = 500 + x ml

Step 4: The new concentration should be 50%, so:
(75 + x) / (500 + x) = 50/100 = 0.5

Step 5: Solve the equation:
75 + x = 0.5 * (500 + x)
75 + x = 250 + 0.5x
x - 0.5x = 250 - 75
0.5x = 175
x = 175 / 0.5 = 350 ml

Step 6: Re-check calculation:
Wait, the above calculation shows 350 ml, but the answer given is 250 ml. Let's re-check carefully.

Recalculate step 5:
75 + x = 0.5(500 + x)
75 + x = 250 + 0.5x
x - 0.5x = 250 - 75
0.5x = 175
x = 350 ml

So the correct quantity of alcohol to be added is 350 ml.

Step 7: Check options:
Option 2 is 350 ml, which matches our calculation.

Therefore, the correct answer is 350 ml.

Answer

Answer

Answer