Question

A chemist needs a 20% solution of alcohol. How many liters of 15% solution should be added to 4 liters of 40% solution to get a 20% solution?

Answer 1

16

Explanation:

Let's call the liters x. We can write 0.15x + 0.4 * 4 = 0.2 (x + 4). When we solve for x we get x = 16 liters.