11-5 Making Predictions

Warm UpWarm Up

Lesson PresentationLesson PresentationProblem of the DayProblem of the Day

Lesson QuizzesLesson Quizzes

11-5 Making Predictions

Warm UpSolve each proportion.1. Which represents a greater amount–0.04 or 3.9

percent?

2. A bag contains 9 lettered tiles. There are 5 Es, 3 Ts, and 1 X. What letter would you be most likely to draw?An E

0.04

11-5 Making Predictions

Problem of the Day

After several tries, Carla figures that the probability of her flipping a playing card into a hat is . If she was successful on 3 tries, how many times did she miss?21

1 8

11-5 Making Predictions

SWBAT use probability to predict events.

11-5 Making Predictions

Vocabularyprediction

11-5 Making Predictions

A prediction is something you can reasonably expect to happen in the future. Weather forecasters use several different methods of forecasting to make predictions about the weather.One way to make a prediction is to use probability.

11-5 Making Predictions

Lawrence finds the experimental probability of his reaching first base is 40%. Out of 350 at-bats, how many times can he expect to reach first base?

Additional Example 1: Using Experimental Probability to Make Predictions

Multiply the probability by the number of at bats.· 350 = x4

10

Method 1: Set up an equation.

140 = x

11-5 Making Predictions

Think: 4 out of 10 is how many out of 350.

Method 2: Set up a proportion.

The cross products are equal.

Multiply.

4 · 350 = 10 · x

Lawrence can predict that he will reach first base about 140 of 350 times.

Additional Example 1 Continued

1400 = 10xDivide each side by 10 to isolate the variable.

140 = x10 10

4 10 = x

350

11-5 Making Predictions

Malia finds the experimental probability of her scoring a goal is 20%. Out of 225 attempts, how many times can she expect to score a goal?

Check It Out: Example 1

Multiply the probability by the number of attempts.· 225 = x2

10

Method 1: Set up an equation.

45 = x

11-5 Making Predictions

Think: 2 out of 10 is how many out of 225.

Method 2: Set up a proportion.

The cross products are equal.

Multiply.

2 · 225 = 10 · x

Malia can predict that she will score about 45 goals of 225 attempts.

Check It Out: Example 1 Continued

450 = 10xDivide each side by 10 to isolate the variable. 45 = x

10 10

2 10 = x

225

11-5 Making Predictions

A spinner has eight sections of equal size. Three sections are labeled 1, two are labeled 2, and the others are labeled 3, 4, and 5. In 50 spins, how often can you expect to spin a 1?

Additional Example 2: Using Theoretical Probability to Make Predictions

3 · 50 = 8 · x

P(spinning a 1) = 3 8

Think: 3 out of 8 is how many out of 50.

18.75 = x

3 8 = x

50The cross products are equal.Multiply150 = 8x

You can expect to spin a 1 about 19 times.

8 8 Divide each side by 8 to isolate the variable.

11-5 Making Predictions

Round to a whole number if it makes sense in the given situation.

Helpful Hint

11-5 Making Predictions

A spinner has eight sections of equal size. Three sections are labeled 1, two are labeled 2, and the others are labeled 3, 4, and 5. In 50 spins, how often can you expect to spin a 2?

Check It Out: Example 2

P(spinning a 2) = 2 8

Think: 2 out of 8 is how many out of 50.The cross products are equal.Multiply. Divide each side by 8 to isolate the variable.You can expect to spin a 2 about 13 times.

2 · 50 = 8 · x

12.5 = x

2 8 = x

50

100 = 8x8 8

11-5 Making Predictions

The Singh family is planning a 7-day tropical vacation during July or August. The island destination they have chosen averages 21 rainy days during this 62-day period. If the Singhs would like to avoid rain on at least 5 days of their vacation, should they go to this spot or choose another?

Additional Example 3: Problem Solving Application

11-5 Making Predictions

11 Understand the Problem

The answer will be whether the Singh family should go to the island.

List the important information:

• The island destination averages 21 rainy days out of 62 days.

• The Singhs want to avoid rain on at least 5days of their vacation.

Additional Example 3 Continued

11-5 Making Predictions

22 Make a PlanOn average 21 out of the 62 days it is rainy. Afterfinding out the number of rainy days there shouldbe forecast, subtract to find the number of notrainy days.

Additional Example 3 Continued

11-5 Making Predictions

Solve33Additional Example 3 Continued

Think: 21 out of 62 is how many out of 7.

The cross products are equal.

Multiply.

21 · 7 = 62 · x

7 – 2 = 5

21 62 = x

7

Divide each side by 62 to isolate the variable.

147 = 62x

2.37 ≈ x There will be more than 2 rainy days in 7 days.Subtract the predicted number of rainy days from the total vacation days.

62 62

11-5 Making Predictions

Look Back44They should choose a different location. It islikely to rain more than 2 days (about 2.4 days)during a 7-day period, which will not give theSinghs at least 5 sunny days.

Additional Example 3 Continued

21 rainy days 62 total days ≈ 20

60 or 33%

2.4 rainy days 7 total days ≈ 2

7 or 30%

Since both ratios are about 30%, the answer isreasonable.

11-5 Making Predictions

The Reid family is planning a 9-day winter vacation during December or January. The destination they have chosen averages 35 snow days during this 60-day period. If the Reids would like to avoid snow on at least 4 days of their vacation, should they go to this spot or choose another?

Check It Out: Example 3

11-5 Making Predictions

11 Understand the Problem

The answer will be whether the Reid family should go to the destination.List the important information:

• The destination averages 35 snow days out of 60 days.• The Reids want to avoid snow on at least 4days of their vacation.

Check It Out: Example 3 Continued

11-5 Making Predictions

22 Make a Plan

On average 35 out of the 60 days it is snowing. After finding out the number of snow days there should be forecast, subtract to find the number of not snow days.

Check It Out: Example 3 Continued

11-5 Making Predictions

Solve33Check It Out: Example 3 Continued

Think: 35 out of 60 is how many out of 9.

The cross products are equal.

Multiply.

35 · 9 = 60 · x

9 – 5 = 4

35 60 = x

9

Divide each side by 60 to isolate the variable.

315 = 60x

5.25 = x There will be more than 5 snow days in 9 days.

Subtract the predicted number of snow days from the total vacation days.

60 60

11-5 Making Predictions

Look Back44They should choose a different location. It islikely to snow more than 5 days during a 9-day period, which will not give the Reids at least 4 days without snow.

Check It Out: Example 3 Continued

35 snow days 60 total days ≈ 35

60 or 58%

5.25 snow days 9 total days ≈ 5

9 or 55%

Since both ratios are about 55%, the answer isreasonable.

11-5 Making Predictions

Standard Lesson Quiz

Lesson Quizzes

Lesson Quiz for Student Response Systems

11-5 Making PredictionsLesson Quiz: Part I

1. The experimental probability of Maura shooting a goal in field hockey is 12%. Out of 300 shots, how many can Maura predict will be goals?

2. If Scott flips two quarters 25 times, how many

times can he expect to flip two heads?6 times

32

11-5 Making PredictionsLesson Quiz: Part II

3. The Aurelio family is planning a 12-day skiing trip during December or january. The region they have chosen gets the right conditions for skiing 46 days during the 62-day period. The Aurelios would like to spend at least 8 days skiing. Will their destination be a good choice?Yes. There will be at least 8 days with the right conditions for skiing.

11-5 Making Predictions

1. Katia finds the probabilty that the traffic light is red when she reaches an intersection is 45%. In one month, she goes through the intersection 65 times. How many times can she expect the light to be red when she reaches the intersection?

A. 22

B. 26

C. 30

D. 45

Lesson Quiz for Student Response Systems

11-5 Making Predictions

2. If you roll a number cube 12 times, about how many times do you expect to roll a number less than five?

A. 6

B. 8

C. 10

D. 12

Lesson Quiz for Student Response Systems