How much water is to be added to 75 ml of alcohol, so that the mixture contains 20% of alcohol?

Correct option is B

Given:
Volume of alcohol = 75 ml

Required alcohol percentage in final mixture = 20%

We need to find the amount of water to be added.

Formula Used:
Let total volume of the final mixture be x ml.
Since alcohol is 20% of the final mixture:

​$$\frac{\text{Alcohol Volume}}{\text{Total Mixture Volume}} = \frac{\text{Required Alcohol Percentage}}{100}$$​​

Solution:

​$$\frac{75}{x} = \frac{20}{100}$$

$$75 \times 100 = 20x \\7500 = 20x \\x = \frac{7500}{20} = 375$$

$$\text{Water to be added} = x - 75 = 375 - 75 = 300$$

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