How much of each item must be mixed to get 7 cups of a mixture that is 7.6 % sodium​ hypochlorite?

Question

A bleach is

6.25​%

sodium hypochlorite and swimming pool shock treatment is

9.5​%

sodium hypochlorite. How much of each item must be mixed to get

7

cups of a mixture that is

7.6 %

sodium​ hypochlorite?

Answer 1

If you don't like the alligation method previously mentioned, try this.

(x cups)(6.25%) + (7-x cup)(9.5%) = (7 cups)(7.6%)

6.25x + 66.5 - 9.5x = 53.2

-3.25x = -13.3

x = 4.1 cups of 6.25% + 2.9 cups of 9.5%