saline solution

[karliekay]

How much of a 40% saline solution must be added to 10 liters of a 25% saline solution to strenghten it to a 30% solution?


I have no clue how to start this. I dont know if I need a formul or what? Please help me.

 

[masters]

How much of a 40% saline solution must be added to 10 liters of a 25% saline solution to strenghten it to a 30% solution?


I have no clue how to start this. I dont know if I need a formul or what? Please help me.

Hi karliekay,

Sometimes it's easier to see these mixture type problems if we put the information in a table:

               | liters  | % saline | total liters |
---------------------------------------------------|
| 40% solution |    x    |    40%   |    40% x     |
---------------------------------------------------|
| 25% solution |   10    |    25%   |    25% (10)  |
---------------------------------------------------|
| 30% solution | x + 10  |    30 %  | 30%(x + 10)  |
---------------------------------------------------|

\(\displaystyle .40x+.25(10)=.30(x+10)\)

Solve for x.

 

[karliekay]

Thanks, seeing it that way really helps. It makes it a lot easier to see what to do.