Question

A scientist needs 1.8 liters of a 22% alcohol solution. She has available a 33% and a

17% solution. How many liters of the 23% and how many liters of the 17%
solutions should she mix to make the 22% solution?

Answer 1

Explanation:

the approach of the other answer is basically correct, but we need to use the correct numbers.

so, I assume that the 33% of the first solution is correct, and not the 23% mentioned later.

x = liters of the 33% solution.

y = liters of the 17% solution.

we know that

x + y = 1.8

and therefore

x = 1.8 - y

and then we want to enforce the desired result (ab% are simply 0.ab)

0.33x + 0.17y = 0.22×1.8

we use the identity from above in this equation :

0.33(1.8 - y) + 0.17y = 0.396

0.594 - 0.33y + 0.17y = 0.396

0.198 - 0.16y = 0

0.198 = 0.16y

y = 1.2375 liters

x = 1.8 - y = 1.8 - 1.2375 = 0.5625 liters

if the first solution is truly only 23%, then we only need to change the number :

0.23(1.8 - y) + 0.17y = 0.396

0.414 - 0.23y + 0.17y = 0.396

0.018 - 0.06y = 0

0.018 = 0.06y

y = 0.3 liters

x = 1.8 - y = 1.8 - 0.3 = 1.5 liters