Question

Mrs, Hansen usually makes a disinfecting solution by adding 1 2/3 cups of bleach to 5 gallons of water. Today, however, she is using only 3 1/2 gallons of water. She wants to make the solution so that it has the same disinfecting strength. How much bleach should she use?

Answer 1

1 1/6 cups

Explanation:

You want to know the amount of bleach to use with 3 1/2 gallons of water to obtain the same strength as 1 2/3 cups of bleach in 5 gallons of water.

Proportion

The quantities are proportional, so the amount of bleach (b) will need to be ...

b/(3 1/2 gal) = (1 2/3 cups)/(5 gal)

Multiplying by 3 1/2 gal, we get ...

b = (3 1/2)(1 2/3)/5 cups = 1 1/6 cups

Mrs. Hanson should use 1 1/6 cups of bleach in 3 1/2 gallons of water.