Computing a percent mixture

Question

A chemist mix is 75 mL of a solution that is 15% acid with 175 mL of a solution that is 75% acid. How many milliliters of acid are in the resulting mixture? What percentage of the resulting mixture is acid?

Answer 1

15(75) + 75(175) = X(175+75), solve for X= percentage of the mixture

190(75) = 250X

X = 19(75)/25 = 19(3) = 57% acid for the mixture

You're using over twice as much of the 75% acid, so you'd expect the mixture to be closer to 75 than to 15, something substantially more than the average of 45

175/75 = 7/3 times more 75% than 15%

75-57 = 18 while 57-15= 42

42/18 = 7/3