9. Orange paint is made by mixing 4 parts yellow paint with 5 parts red paint. If Mr. Connor wants to have 27 total gallons of paint, how many gallons of red paint will he need to use?

Answer 1

With ratios you use parts/whole and can solve by setting the ratios equal to each other:

5/(4 + 5) = x / 27

5/9 = x / 27

27 * 5 = 9x

135 = 9x

15 = x

15 gallons of red paint.