A druggist has two mixtures of a certain chemical and water, one containing 10% of the chemical and the other containing 40% of the chemical. How much of each mixture should he use to make 10 ounces that contain 25% of the chemical? How many ounces of chemical are in the final mixture?

Let x be the amount of the solution containing 10% of the chemical. Then, the solution with 40% chemical becomes 10 - x. The equation for balancing the chemical content of the solution is,

0.10x + 0.40 (10 - x) = 0.25 (10)

The value of x is 5. Hence, the druggist should mix 5 ounces of each. There are 2.5 ounces of chemical in the final mixture.