Proportions

PROPORTIONS and RATIOS

OBJECTIVES

SWBAT find missing measures, sides and angles by writing and solving ratios and proportions.

RATIO

​Setting up ratios

​You need to read the problem carefully so you can determine what is being asked. In the top problem the ratio of red to green is 1:2 or 1/2. The ratio of green to red would be 2:1 or 2/1.

In the bottom problem the ratio of red to greenis 1:3. The ratio of green to red is 3:1

THE ORDER IS IMPORTANT!!!!

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I love apples!

​What is the ratio of green apples to red apples?

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​What is the ratio of red apples to non-red apples?

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​What is the ratio of yellow apples to green apples?

Cupcakes!

​What is the ratio of red cupcakes to blue cupcakes?

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​What is the ratio of orange cupcakes to non-orange cupcakes?

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​What is the ratio of non-green cupcakes to blue cupcakes?

Multiple Choice

In a class of 23 students, 8 have blue eyes. What is the ratio of blue-eyed students to non-blue-eyed students?

• 15:8

• 23:8

• 8:23

• 8:15

Multiple Choice

42 teachers at MRHS have dogs and 37 have cats. What is the ratio of pet owners to dog owners?

• 42:37

• 42:79

• 79:42

• 37:42

Means and Extremes

• The product of the means equals the product of the extremes

• The means are the bottom of the first and the top of the second

• The extremes are the top of the first and the bottom of the second

CROSS PRODUCTS

Open Ended

Please find m.

$$\frac{78}{m}=\frac{90}{36}$$  

Open Ended

Please find y.


$$\frac{6}{18.2\ }=\frac{9}{y}$$     

Open Ended

Please find x

$$\frac{4x-5}{3}=-\frac{26}{6}$$  

UNIT RATIO

A ratio in which the denominator equals 1

Finding angles or sides of triangles using ratios.

The ratio of the angles of a triangle is 1:3:8. What is the measure of each angle?

Multiple Choice

The ratio of the angles of a pentagon is 3:3:4:5:5. Please find the measure of the smallest angle.

• 27

• 20

• 81

• 540