Ratios and proportions compare two items or groups of items. A proportion exists when two ratios are equivalent, or equal. To check if two ratios form a proportion, you can use cross products - multiplying the numbers across each ratio. If the products are equal, the ratios are proportional. Another method is using a scale factor, where you multiply each number in one ratio by the same amount. If multiplying maintains the equality between the ratios, they form a proportion.

1. Ratios and Proportions

3. How do you write equivalent ratios?

4. To check if 2 ratios are proportional…you can use cross products or cross multiplying = Is 2 x 10 equal to 4 x 5? If yes, you have a proportion!

5. You try it! Is this a proportion? =

6. You can also use “scale factor” to see if two ratios form a proportion = x 3 = x 3 = Since 3 x 3 = 9 and 8 x 3 = 24, these ratios do form a proportion! 3 is called the “scale factor”.

7. You Try it! Is this a proportion? =

8. You Try it! Is this a proportion? =