Scientist with two solutions

Question

One solution is A the other is B each contain salt

Solution A is 40% salt ..... Solution B is 90% salt

She wants 180 ounces of a mixture that is 80% salt.. how much of each solution does she need?

Answer 1

Let a = number of oz of the 40% salt and b = number of oz of the 90% salt

Then

(a(40) + b(90))/(a+b) = 80

and a + b = 180

or 40a + 90(180-a) = 80*180 Solve for a = 36 then b = 144

Check: (40(36) + 90(144))/(36+144) = 80 YES!