Learning Target: I can determine whether two quantities are in proportion.
Testing for Proportional Relationships
Two quantities are in proportion if the ratios between their values are always the same.
Look at this table:
Are the two quantities in proportion?
You can set up the ratios between each pair of values and find out:
6/9 ≟ 10/15 ≟ 8/12 ≟ 4/6
Simplify each ratio to see if they are all equal.
2/3 = 2/3 = 2/3 = 2/3
Since all the ratios are equal, the quantities are in proportion.
You can also determine if two quantities are in proportion by using a graph. Let one quantity be the x-values and the other be the y-values, and graph them as points on the coordinate plane. If the points form a straight line that goes through the origin (0, 0), the quantities are in proportion.
The points make a line that goes through the origin. The quantities are in proportion.
Let's Practice Together
For each table or chart below, determine whether the quantities are in proportion.
1. 
2. 
Your Turn
3. 
4. 
5. 
Check for Understanding
1. Four friends are baking cookies for a fund raiser. Each one is baking a different number of cookies, but there is a proportional relationship between the number of cookies baked and the amount of flour used.
- Samantha is baking 16 cookies and uses 2 cups of flour.
- Roscoe is baking 40 cookies and uses 5 cups of flour.
- Chris is baking 32 cookies and uses 3 cups of flour.
- Tyra is baking 48 cookies and uses 6 cups of flour.
Which one is not using the correct amount of flour?
Answers
1. no
2. yes
3. yes
4. no
5. no
Check for Understanding
1. Chris
