Question

You have 15 milliliters of a drink that contains 15% milk. How many millimeters of a drink containing 63% milk needs to be added in order to have a final drink that is 45% milk?

Answer 1

4 ml of the 63% milk drink

Explanation:

Multiplying 15 ml by 0.15 results in 2.25 ml, the amount of whole milk in the drink. Let m represent the number of ml of a drink that is 63% milk.

The final amount of milk drink that is to be 45% milk will be 15 ml + m, and the amount of whole milk contained in this drink will be 0.45(15 + m).

Then:

0.15(15 ml) + 0.63(m) = 0.45(15 + m), where m is to be in milliliters.

2.25 + 0.63m = 6.75 + 0.45m

First: consolidate the m terms on the left. 0.63m less 0.45m yields 18 m; then we have:

2.25 + 18m = 6.75, or

18 m = 4.50, or m = 4 ml.

In conclusion: adding 4 ml of that 63% milk drink to the initial 15 ml of 15% milk will result in (15 ml + 4 ml) of a 45% milk drink.