A certain shade of paint is made by mixing 5 parts blue paint with 2 parts white paint. To get the same shade of paint how much white paint should be mixed with 8.5 quarts of blue paint?

The concept that is useful to answering the question above is the ratio - proportion. Let x be the number of white paint that should be used in the mixture. The ratio - proportion expression of the given above is,

5 parts / 2 parts = 8.5 quarts / x quarts

Solving for x gives an answer of x = 3.4. Thus, 3.4 quarts of white paint should be used for the mixture.