1. 7.1 Ratio and Proportions Pg 356
Objective: Student will solve problems by writing and solving proportions.
How do you use ratios and proportions to solve a problem?

2. Ratio of a to b
A ratio is a comparison of two numbers a to b and is written as a fraction of a/b.
Can be written three ways
a:b
* b cannot = 0, because the denominator cannot be 0.
Always write ratios in simplified form! (reduce the fraction!) a b
a to b

3. Example: simplify.

4. Ex. 2 In the diagram AB : BC is 4 : 1 and AC = 30. Find AB and BC.
4x + x = 30 B C
5x = 30 A
x = 6
AB = 4(6) = 24
BC = 6

5. Ex. 3 The perimeter of a rectangle is 80 ft
Ex.3 The perimeter of a rectangle is 80 ft.The ratio of the length to the width is 7:3. Find the length and the width of the rectangle.
P = 2L + 2W
14x + 6x = 80
W = 3x
20x = 80
x = 4
L = 7x
L = 7x = 7(4) Length = 28ft
W = 3x = 3(4) Width = 12 ft

6. Guided Practice
Work Problems 32 and 37

7. Assignment
Page # 1-8, and odd

8. Proportion
An equation stating 2 ratios are =

9. Proportions – An equation where 2 ratios are equal to each other.
b and c are the means. a b = c d
a and d are the extremes.
Cross Product Property – The product of the extreme is equal the product of the means.
bc = ad a b = c d
, then If

10. Example
10(s-5)=4s
10s-50=4s
-50= -6s

11. Assignment Page 361-363 #, 14-36 even and 38-45.
Let work 38 and 39 together.