Question

You need 320 mL of a 85% alcohol solution. On hand, you have a 60% alcohol mixture. How much of the 60% alcohol mixture and pure alcohol will you need to obtain the desired solution?

You will need
____ mL of the 60% solution
and
_____ mL of pure alcohol.

Answer 1

Explanation:

If we let x = the amount of 5% solution and y = the amount of pure alcohol, we can set up that

.05x+y is the amount of alcohol in our resulting mixture, and x+y is the total amount in our resulting mixture (which we know is 380)

so we also know that:

(.05x+y)/380 = .6

If we simplify this we come up with:

.05x+y=228

and we know x+y=380

If we solve this as a system of equations, we will find that:

x=160 ml

y=220 ml