You need a 90% alcohol solution. On hand, you have a 55 mL of a 45% alcohol mixture. You also have 95% alcohol mixture. How much of the 95% mixture will you need to add to obtain the desired solution?

495 milliliters of the 95% mixture are needed.

Step-by-step explanation:

Given that I need a 90% alcohol solution, and on hand I have a 55 ml of a 45% alcohol mixture, and I also have 95% alcohol mixture, to determine how much of the 95% mixture will I need to add to obtain the desired solution, the following calculation must be performed:

55 x 0.45 + 45 x 0.95 = 67.5

25 x 0.45 + 75 x 0.95 = 82.5

15 x 0.45 + 85 x 0.95 = 87.5

10 x 0.45 + 90 x 0.95 = 90

10 = 55

90 = X

90 x 55/10 = X

4,950 / 10 = X

495 = X

Thus, 495 milliliters of the 95% mixture are needed.