How do you make a solution that 85% salt from 2 solutions one has 90% salt and the other has 65% salt?

Question

Mixture calculation 

Answer 1

Since it is not specified how much of the 85% solution there is to be, 

there are many ways to do it.

 

Here is one way it can be done.

 

Mix 100 mL of the 90% salt with 25 mL of the 65% salt.

 

The salt concentration is then 90% * 100 + 65% * 25 = 90 + 16.25 mL = 106.25 mL of salt

   which is contained is 150 mL of solution.

 

That is 106.25/125 =  0.85 = 85%