Exemple !

At a store 4 breads and 3 yogurts costs $ 20. At another store 4 breads and 5 yogurts costs $ 28.

How much does a bread cost?

How much does a yogurt cost?

The problem can be solved with the comparison method.

The data will be grouped as follows:

4 breads ... 3 yogurts ... $ 20

4 breads ... 5 yogurts ... $ 28

We notice that the difference in money comes from the number of yogurts purchased

Thus 5 - 3 = 2 yogurts and 28 - 20 = 8 $

So 2 yogurt costs $ 8, then a yogurt costs 8 : 2 = $ 4

So 3 yogurt costs 3 x 4 = $ 12

20 - 12 = $ 8 costs 4 breads

So 4 breads costs $ 8, then a bread costs 8 : 4 = $ 2