a pharmacist has a 40% acid solution and has a 25% acid solution. How many liters must be mixed to form 54 liters of a 27 % acid solution?
Karen, this problem can be worked easily with algebra; however, I saw a post by Mathmate a week or so ago that solved the problem easily with a trick. Here it is.
25%.....27%.....40%
....2........13.....difference
Make a large X connecting 25 with 13 and 40 with 2. That tells you that you want 2 parts of 40% + 13 parts of 25%. How much is a part? That is 54L/15 = 3.6L.
So 2*3.6L = 7.2 L of the 40% + 13*3.6 = 46.8 L of 25% to make 54L of 27%.
If you want to do it by algebra, then
let x = volume of 40% and 54-x = volume of 25%.
40x + 25(54-x) = 27*54
Solve for x and 54-x.