You need a 45% alcohol solution. On hand, you have a 225 mL of a 85% alcohol mixture. How much pure water will you need to add to obtain the desired solution?

Question

You need a 45% alcohol solution. On hand, you have a 225 mL of a 85% alcohol mixture. How much pure water will you need to add to obtain the desired solution?

A) Write an equation using the information as it is given above that can be used to solve this problem. Use X as your variable to represent the amount of pure water you need to use.
Equation:

Answer 1

The equation can be written as follows:

0.85(225) + 0(X) = 0.45(225 + X)

Answer 2

The equation can be written as:

0.85(225 mL) + 0(X mL) = 0.45(225 mL + X mL)