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?

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

Example: simplify.

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

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

Guided Practice Work Problems 32 and 37

Assignment Page 361-363 # 1-8, and 13-37 odd

Proportion An equation stating 2 ratios are =

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

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

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