Mrs. huang operates a soybean farm. she buys many supplies in bulk. often the bulk products need to be custom mixed before mrs. huang can use them. to apply herbicide to a large field she must mix a solution of 67% herbicide with a solution of 46% herbicide to form 42 liters of a 55% solution. how much of the 67% solution must she use? a.18 l b.34 l c.35 l d.23 l

To solve this problem, let us first assign variables. Let us say that:

x = volume of 67% herbicide solution

y = volume of 46% herbicide solution

The total volume should be 42 liters therefore:

x + y = 42

x = 42 – y                                             --> 1

The component mass balance on the pure herbicide would be:

0.67 x + 0.46 y = 0.55 (42)              --> 2

Substituting equation 1 to 2:

0.67 (42 – y) + 0.46 y = 23.1

28.14 – 0.67 y + 0.46 y = 23.1

- 0.21 y = - 5.04

y = 24 L

Calculating for x using equation 1:

x = 42 – 24

x = 18 L

Therefore we only need 18 L of the 67% herbicide solution.

A. 18 L