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- Количество слайдов: 52

Alan S. Tussy R. David Gustafson Prealgebra Second Edition Copyright © 2002 Wadsworth Group. 1

8. 1 Ratio In this section, you will learn about • Ratios • Rates • Unit rates • Unit costs 2

Real-life ratios 3

Ratios 4

EXAMPLE 2 Carry-on luggage. Airlines allow passengers to carry a piece of luggage onto an airplane only if it will fit in the space shown in Figure 8 -1. What is the ratio of the length of the space to its width? 5

Rates 6

Rates 7

Unit rates 8

Computing gas mileage 9

Unit costs 10

EXAMPLE 7 Comparison shopping. Olives come packaged in a 10 -ounce jar, which sells for $2. 49, or in a 6 -ounce jar, which sells for $1. 53. (See Figure 8 -3. ) Which is the better buy? 11

8. 2 Proportions In this section, you will learn about • Proportions • Means and extremes of a proportion • Solving proportions • Writing proportions to solve problems 12

Ladders - the 4 -to-1 rule 13

Proportions 14

Means and extremes of a proportion 15

Means and extremes of a proportion 16

Solving proportions 17

Solving proportions with a calculator 18

Writing proportions to solve problems EXAMPLE 6 Grocery shopping. If 5 apples cost $1. 15, how much will 16 apples cost? 19

EXAMPLE 7 Scale drawing. A scale is a ratio (or rate) that compares the size of a model, drawing, or map to the size of an actual object. On the next page, the airplane in Figure 85 is drawn using a scale of 1 inch: 6 feet. This means that 1 inch on the drawing is actually 6 feet on the plane. The distance from wing tip to wing tip (the wingspan) on the drawing is 5 inches. What is the actual wingspan of the plane? 20

EXAMPLE 7 Scale drawing. 21

8. 3 American Units of Measurement In this section, you will learn about • American units of length • Converting units of length • American units of weight • American units of capacity • Units of time 22

American units of length 23

EXAMPLE 1 Measuring the length of a nail. To the nearest ¼ inch, find the length of the nail in Figure 8 -7. 24

EXAMPLE 2 Measuring the length of a paper clip. To the nearest ⅛ inch, find the length of the paper clip in Figure 8 -8. 25

EXAMPLE 3 Measuring the length of a ticket. Find the length of the tear-off part of the concert ticket in Figure 8 -9. 26

Converting units of length 27

Finding the length of a football field in miles 28

American units of weight 29

Finding the weight of a car in pounds 30

American units of capacity 31

Units of time 32

EXAMPLE 9 Astronomy. A lunar eclipse occurs when the Earth is between the sun and the moon in such a way that the Earth’s shadow darkens the moon. See Figure 8 -10 (which is not to scale). A total lunar eclipse can last as long as 105 minutes. How many hours is this? 33

8. 4 Metric Units of Measurement In this section, you will learn about • Metric units of length • Converting units of length • Metric units of mass • Metric units of capacity • Cubic centimeters 34

Metric units of length 35

Metric ruler 36

EXAMPLE 1 Measuring the length of a nail. To the nearest centimeter, find the length of the nail in Figure 8 -13. 37

EXAMPLE 2 Measuring the length of a paper clip. To the nearest ⅛ inch, find the length of the paper clip in Figure 8 -8. 38

EXAMPLE 2 Measuring the length of a paper clip. To the nearest millimeter, find the length of the paper clip in Figure 8 -8. 39

Converting units of length 40

Converting units of length 41

Metric units of mass 42

Metric units of capacity 43

Metric units of capacity 44

Cubic centimeters 1 m. L = 1 cm 3 = 1 cc 5 cc = 5 m. L 1, 000 cc = 1, 000 m. L = 1 liter 45

8. 5 Converting between American and Metric Units In this section, you will learn about • Converting between American and metric units • Comparing American and metric units of temperature 46

Converting between American and metric units 47

EXAMPLE 1 Clothing label. Figure 8 -17 shows a label sewn into some pants made in Mexico for sale in the United States. Express the waist size to the nearest inch. 48

Equivalent Weights and Masses 49

Equivalent Capacities 50

Comparing American and metric units of temperature 51

Conversion formulas for temperature 52