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Lesson 3

What are probabilities?

Unit 8

Probability and Sampling

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3.1 Warm Up: Which Game Would You Choose?

Which game would you choose to play? Explain your reasoning.

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Learning Targets

  • Today I will learn how to calculate the probability of simple events.

  • I can use the sample space to calculate the probability of an event when all outcomes are equally likely.
  • I can write out the sample space for a simple chance experiment.

Success Criteria

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3.2 What’s Possible?

a. Han rolls a standard number cube once.

b. Clare spins this spinner once.

c. Kiran selects a letter at random from the word “MATH.”

d. Mai selects a letter at random from the alphabet.

e. Noah picks a card at random from a stack that has cards numbered 5 through 20.

1. For each situation, list the sample space and tell how many outcomes there are.

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3.2 What’s Possible?

a. Is Clare more likely to have the spinner stop on the red or blue section?

b. Is Kiran or Mai more likely to get the letter T?

c. Is Han or Noah more likely to get a number that is greater than 5?

3. Suppose you have a spinner that is evenly divided showing all the days of the week. You also have a bag of papers that list the months of the year. Are you more likely to spin the current day of the week or pull out the paper with the current month?

2. Next, compare the likelihood of these outcomes. Be prepared to explain your reasoning.

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3.2 Are you ready for More?

Are there any outcomes for two people in this activity that have the same likelihood? Explain or show your reasoning.

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3.3 What’s in the Bag?

Your teacher will give your group a bag of paper slips with something printed on them.Repeat these steps until everyone in your group has had a turn.

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3.3 What’s in the Bag?

1. How was guessing the sample space the fourth time different from the first?

2. What could you do to get a better guess of the sample space?

3. Look at all the papers in the bag. Were any of your guesses correct?

4. Are all of the possible outcomes equally likely? Explain.

5. Use the sample space to determine the probability that a fifth person would get the same outcome as person 1.

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Lesson Summary

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3.4 Cool Down: Letter of the Day

A mother decides to teach her son about a letter each day of the week. She will choose a letter from the name of the day. For example, on Saturday she might teach about the letter S or the letter U, but not the letter M.

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Reflections

  • Can you use the sample space to calculate the probability of an event when all outcomes are equally likely?
  • Can you write out the sample space for a simple chance experiment?

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Practice Problems

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Lesson Video

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