1. October 1, 2012 Ratios and Proportions
Warm-up: Solve for x
1. 3(x + y) = a x – 2y = z
x – 9 = -2x + 1
HW 3.6: Pg. 158 #19-35odd, 40-45all
Quiz last class this week!

2. Lesson 3.6 Ratios and Proportion
A ratio is a comparison of two numbers by division. (A fraction)
Example: Ratio of 2 to 5 means:
2: or
Ex 1: Write a ratio 2 ways for the following:
The Halloween dance had a ratio of 3 boys to 6 girls.

3. Ex 2: Are these equivalent ratios that form a proportion?
A proportion is an equation that states two ratios are equivalent (equal).
are equivalent ratios and form a proportion.
Ex 2: Are these equivalent ratios that form a proportion?
a) b) c)

4. How do you solve a proportion?
Ex 3: Solve.
Use cross multiplying

5. Individual Practice
Solve the proportion.

6. Example 4
original recipe
new recipe
A recipe for pumpkin pie requires 5 tablespoons of nutmeg and 3 cups of pumpkin. Kayla needs to make enough to pies to feed a small army, so she plans to use 24 cups of pumpkin. How much nutmeg does she need to keep it proportional?

7. Example 5
Charles goes on a 30-mile bike ride every Saturday. He rides the distance in 4 hours. At this rate, how far can he ride in 6 hours?

8. Your turn…
The scale of a map for Crater Lake National Park is 2 inches = 9 miles. The distance between Discovery Point and Phantom Ship Overlook on the map is about 1 ¾ inches. What is the distance between these two places?