Question

Silvia wants to mix a 20% apple juice drink with pure apple juice to make 4 L of a juice drink that is 80% apple juice. How much pure apple juice should she use?​

Answer 1

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Answer:

  3 liters

Step-by-step explanation:

There's a simple and effective "visual" way to solve mixture problems that makes short work of this.

In the attached, the concentrations of the contributors are listed on the left. It can work well to put the largest contributor on top (though that is not strictly necessary). The target concentration is put in the middle between them, and the differences along the diagonals are computed.

The diagonal differences are reduced to lowest terms as a ratio in the right-hand column. These numbers can be compared to the problem statement to see how they relate.

In this case, the total is 4 L of juice, and the total of the ratio units is 4. Then the ratio units are the number of liters of the corresponding contributor:

• 3 L of 100% juice
• 1 L of 20% juice