7th Grade Math

Chapter Study Guide and Review

478 Probability and Predictions

Multi-Part Lesson Review

Probability

Probability (Lesson 1A)

A bag of animal crackers contains 5 monkeys,

4 giraffes, 6 elephants, and 3 tigers. Suppose

you draw a cracker at random. Find the

probability of each event. Write as a fraction

in simplest form.

8. P(monkey)


9. P(tiger)


10. P(giraffe or elephant)


11. P(not monkey)


12. P(monkey, giraffe, or elephant)


13. ARRIVALS The probability that a plane
    will arrive at the airport on time is _^2325.
    Find the probability that the plane will
    not arrive on time. Write as a percent.

EXAMPLE 1 What is the probability of

rolling a number less than 3 on a number

cube? Write as a fraction in simplest form.

P(1 or 2) = ___total number of possible outcomesnumbers less than 3

= _^26 Two numbers are less than 3.

= _^13 Simplify.

So, P(1 or 2) = _^13.

Sample Spaces (Lesson 1B)

For each situation, find the sample space

using a tree diagram.

14. rolling a number cube and tossing a coin


15. choosing from pepperoni, mushroom, or
    cheese pizza and water, juice, or milk


16. GAMES Eliza and Zeke are playing a
    game in which Zeke spins the spinner
    shown and rolls a number cube. If the
    sum of the numbers is less than six, Eliza
    wins. Otherwise Zeke wins. Find the
    sample space. Then find the probability
    that Zeke wins.

41

32

EXAMPLE 2 Ginger and Micah are

playing a game in which a coin is tossed

twice. If heads comes up exactly once,

Ginger wins. Otherwise, Micah wins. Find

the sample space. Then find the probability

that Ginger wins.

'JSTU

5PTT

4BNQMF

4QBDF

4FDPOE

5PTT

)

)

5

)

5

))

)5

5)

55

5

There are four equally likely outcomes with

2 favoring each player. The probability that

Ginger wins is _^2

4

or _^1

2

.

Lesson 1

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