How much water is to be added to 75 ml of alcohol so that the mixture contains 25% of alcohol?
100 ml
225 ml
250 ml
125 ml
Answer is Right!
Answer is Wrong!
This question was previously asked in
UPSC CAPF – 2021
The initial mixture is pure alcohol, so it contains 75 ml of alcohol and 0 ml of water, with a total volume of 75 ml.
Let ‘x’ be the amount of water added in ml.
After adding ‘x’ ml of water, the amount of alcohol remains 75 ml, and the total volume of the mixture becomes (75 + x) ml.
The target is for the mixture to contain 25% alcohol.
Percentage of alcohol = (Amount of alcohol / Total volume of mixture) * 100
25 = (75 / (75 + x)) * 100
Dividing both sides by 100:
0.25 = 75 / (75 + x)
Multiply both sides by (75 + x):
0.25 * (75 + x) = 75
18.75 + 0.25x = 75
Subtract 18.75 from both sides:
0.25x = 75 – 18.75
0.25x = 56.25
Divide by 0.25:
x = 56.25 / 0.25
x = 5625 / 25
x = 225
Therefore, 225 ml of water must be added.