Problem solving with two and three variables

Question

How many litres of each 5% and 20% antifreeze must be combined to get 10 litres of solution that is 12.5% antifreeze?

Answer 1

We can set up a system of linear equations. One can represent the total volume of the mixture. The other can represent the total concentration of the mixture. The first will be:

 

x + y = 10, where x = the amount of 5% antifreeze and y = the amount of 20% antifreeze

 

The second equation is:

 

.05x + .20y = 12.5(10)

 

You should now be able to solve this system using either the Elimination or the Substitution Method, Sarah