~ 8.9 ~

Multi-step Experiments

Learning Targets

  • I can use the sample space to calculate the probability of an event in a multi-step experiment.

Notes

Suppose we have two bags. One contains 1 star block and 4 moon blocks. The other contains 3 star blocks and 1 moon block.

If we select one block at random from each, what is the probability that we will get two star blocks or two moon blocks?

To answer this question, we can draw a tree diagram to see all of the possible outcomes.

There are 5 • 4 = 20 possible outcomes. Of these, 3 of them are both stars, and 4 are both moons. So the probability of getting 2 star blocks or 2 moon blocks is 7/20.

In general, if all outcomes in an experiment are equally likely, then the probability of an event is the fraction of outcomes in the sample space for which the event occurs.

Activities

9.2 Spinning a Color and Number

The other day, you wrote the sample space for spinning each of these spinners once.

What is the probability of getting:

  1. Green and 3?

  2. Blue and any odd number?

  3. Any color other than red and any number other than 2?

Add to Your Notes

Remember...For sample spaces where each outcomes is equally likely, the probability of an event can be computed by counting the number out outcomes and dividing by the total number of outcomes in the sample space.

desired outcomes

total outcomes

9.3 Cubes and Coins

  1. Suppose you roll two number cubes. What is the probability of getting:

      • Both cubes showing the same number?

      • Exactly one cube showing an even number?

      • At least one cube showing an even number?

      • Two values that have a sum of 8?

      • Two values that have a sum of 13?

  2. Jada flips three quarters. What is the probability that all three will land showing the same side?

9.4 Pick a Card

Imagine there are 5 cards. They are colored red, yellow, green, white, and black. You mix up the cards and select one of them without looking. Then, without putting that card back, you mix up the remaining cards and select another one.

  1. Write the sample space and tell how many possible outcomes there are.

  2. What structure did you use to write all of the outcomes (list, table, tree, something else)? Explain why you chose that structure.

  3. What is the probability that:

      • You get a white card and a red card (in either order)?

      • You get a black card (either time)?

      • You do not get a black card (either time)?

      • You get a blue card?

      • You get 2 cards of the same color?

      • You get 2 cards of different colors?

Assignment

Check Google Classroom!