Presentation is loading. Please wait.

Presentation is loading. Please wait.

Lesson 6-2 Using Proportions Pgs. 270-274 What you will learn: Solve proportions Use proportions to solve real- world problems.

Similar presentations


Presentation on theme: "Lesson 6-2 Using Proportions Pgs. 270-274 What you will learn: Solve proportions Use proportions to solve real- world problems."— Presentation transcript:

1

2 Lesson 6-2 Using Proportions Pgs What you will learn: Solve proportions Use proportions to solve real- world problems

3 Vocabulary & Key Concept Proportion (270): a statement of equality of two ratios Cross Products (270): From the example, ad & cb are the cross products of the proportion Proportion: A proportion is an equation stating that two ratios are equal Symbol: a = c b d  Example: 2 = 6 3 9

4 Consider this proportion: a = c b d a  bd = c  bd b d ad = cb Simplified to cross products 12 = (168)  84(24) 2016 = 2016 The cross products are equal.

5 Key Concept (271): Property of Proportions Words: The cross products of a proportion are equal. Symbols: If a = c, then ad=bc. If ad=bc, then a = c b d b d

6 Example 1: Identify Proportions Determine whether each pair of ratios forms a proportion. 1, Write a proportion: 1 = Cross Products: 1  16 = 4  4 Simplify: 16 = 16 1 = 4 Yes these are 4 16 proportions 2.1, Write a proportion: 2.1 =  3 Cross Products: 2.1  7 = 3.5  Simplify: 14.7  10.5

7 Example 2: Solve Proportions Solve each proportion. k = k = Cross Products: k  7 = 35  3 Multiply: 7k = 105 Divide: 7k = Solve: k = 15 The solution is 15 3 = 18 t 24 3 = 18 t 24 Cross Products: 3  24 = t  18 Multiply: 72 = 18t Divide: 72 = 18t Solve: t = 4 The solution is 4

8 Example 3: Use a Proportion to Solve a Problem: A 3” x 5” photo is enlarged so that the length of the new photo Is 7 inches. Find the width of the new photo. Explore: You know the photo is 3”x 5” and you know that the length of the new photo is 7”. You need to find the width of the new photo. Plan: Write and solve a proportion using ratios that compare the lengths and widths of the photos. Let w represent the width of the new photo. Solve: length of the old photo = length of the new photo width of the old photo width of the new photo

9 Draw a diagram of the photo, if needed. 3” 5” 7” 5 = 7 3 w 5  w = 3  7 5w = 21 5w = 21w= 4.2 or w 1515

10 Example 4: Convert Measurements Louisville, Ky is home to the world’s largest baseball glove. The glove is 4 feet high, 10 feet long, 9 feet wide, and weighs 15 tons. Find the height of the glove in centimeters if 1ft = 30.48cm. Let h = the height in centimeters Set up a proportion: 1ft = 4ft 30.48cm h cm 1  h =  4 h = The height of the glove is cm.

11 YOU PRACTICE! Determine whether each pair of ratios forms a proportion. A.4, B.18, Solve the proportion. C.W = D. 2 = c Write a proportion that could be used to solve for the variable. Then solve. E.Y dollars for 5.4 gallons 14 dollars for 3 gallons 20  32, not a proportion 36 = 36, yes a proportion W = 7 C = 9.6 y = y= $25.20

12 Now here is a brain tickler. Think logically thru this! Solve the proportion. 3 = m-3 3(m-3) = 14(15) Distributive Property! 3m - 9 = 210 The equation to work with 3m + (-9) = 210 Rewrite the problem so you don’t get confused! 3m + (-9) +9 = 210 Additive Inverse Property (-9) + 9 = 0 3m = m = m = 73 Check: 3 = =  70 = 14  = 210 

13 Extra Practice Sheets Are by the door on your Way out!!


Download ppt "Lesson 6-2 Using Proportions Pgs. 270-274 What you will learn: Solve proportions Use proportions to solve real- world problems."

Similar presentations


Ads by Google