1. Solving Proportions

2. Proportion- an equation that states two ratios are equal
Variable- a symbol, usually a letter, that stands for a number

3. Cross Products- a method used to determine if two ratios form a proportion.
Triangle of Love – cross products divided by the 3rd number

4. The cross products of a proportion are always equal!
News Flash!
The cross products of a proportion are always equal!

5. Example 1:
Do these ratios form a proportion? 3 9 6 18

6. CROSS MULTIPLY!!! 3 9 6 18 54 54
Since the products are equal, the ratios are equal!

7. Example 2:
Do these ratios form a proportion? 2 7 5 13

8. CROSS MULTIPLY!!! 2 7 5 13 26 35
Since the products are not equal, the ratios are not equal!

9. Triangle of Love
Remember the Triangle of Love consist of cross-multiplying and dividing by the 3rd number.

10. Example 3:
Find the value of the variable. Use the “Triangle of Love” 4 18 6 X =

11. 4 18 6 X =

12. Example 4:
Find the value of the variable. m 12 6 9 =

13. Using the Triangle to Solve Part over Whole Problems
The Love Triangle
part
whole

14. Example 5:
A flavor of frozen yogurt has 10 calories in 6 oz. How many calories are in 9 oz. of that frozen yogurt?

15. Setting the Problem Up =
Make sure whatever unit you put on top, it needs to be on top on the other side.
Example 1: oz oz
calories calories =

16. 10 6 X 9 =

17. Example 6: (think part over whole)
Shane’s neighbor pledged $1.25 for every 0.5 miles that Shane swims in the charity swim-a-thon. If Shane swims 3 miles, how much money will his neighbor donate?
(think part over whole)

18. Setting the Problem Up =
Make sure what ever unit you put on top, it needs to be on top on the other side. Example: $ $ Miles Miles =

19. Are these proportions?
Solve for the variable