3 ml of a 35% saline solution was mixed with 4 ml of pure water. find the concentration of the new mixture

Question

This was a question that was on a packet for my liberal arts class i cant figure it out and there is many other word problems he put on here

Answer 1

In general, on these types of problems, you want to set up amount * percent + amount * percent = amount *percent.

For this problem, you have 3 ml * .35 + 4 ml * 0 (pure water = no saline) = 7 ml (the total of 3 +4) * x (the concentration you want to find.

 

So 3 * .35 + 4 * 0 = 7 * x.

1.05 = 7x

.15 = x

 

The new solution is 15% concentration.