A chemist mixes a 25% boric acid solution with a 50% boric acid solution to produce a 40% boric acid solution. How much of each solution is required to obtain a total of thirty liters of the 40% boric acid.

Let the number of Liters of 25% boric acid =B Then, the number of Liters of 50% boric acid =30 - B

0.25B + 0.50[30 - B] =0.40 * 30, solve for B

B = 12 Liters of 25% boric acid. 30 - 12 = 18 Liters of 50% boric acid.