How many ounces of each solution should she use?

Question

A scientist has two solutions, which she has labeled Solution A and Solution B. Each contains salt. She knows that Solution A is 70% salt and Solution B is 95% salt. She wants to obtain 50 ounces of a mixture that is 85% salt. How many ounces of each solution should she use?

Answer 1

70A + 95B = 85(50) = 4250

A +B = 50 multiply by 70 to get

70A + 70B = 3500. Subtract from the 1st equation to get

25B = 750

B = 750/25 = 30 ounces of 95% solution

A = 50-30 = 20 ounces of 70% solution