7th Grade Math

Chapter Study Guide and Review 479

Probability (continued)

Count Outcomes (Lesson 1C)

Use the Fundamental Counting Principle to

find the total number of outcomes for each

situation.

17. rolling two number cubes


18. creating an outfit from 6 different shirts
    and 4 different pants


19. creating a one-flavor, one-topping ice
    cream sundae from 10 flavors of ice
    cream and 6 different toppings


20. SKATEBOARDS World Sports makes
    skateboards with different deck patterns.
    You can choose one of four deck lengths
    and one of six types of wheels. If they
    have 120 different skateboards, how
    many deck patterns are there?

EXAMPLE 3 Use the Fundamental

Counting Principle to find the total

number of outcomes for a coin that is

tossed four times.

There are 2 possible outcomes, heads or

tails, each time a coin is tossed. For a coin

that is tossed four times, there are 2 · 2 · 2 · 2

or 16 outcomes.

EXAMPLE 4 Find the probability that in

a family of four children, all four children

are girls.

There are 16 outcomes. There is one

possible outcome resulting in four girls. So,

the probability that all four children are

girls is _^1

16

.

Permutations (Lesson 1D)

21. PICTURES In how many ways can the
    picture frames shown below be arranged
    in a line on the wall?


22. LETTERS How many permutations are
    there of the letters in the word computer?


23. RUNNING Jacinda and Raul are entered
    in a race with 5 other runners. If each
    runner is equally likely to win, what is
    the probability that Jacinda will finish
    first and Raul will finish second?

EXAMPLE 5 Nathaniel needs to choose

two of the chores shown to do after school.

If he is equally likely to choose the chores,

what is the probability that he will walk

the dog first and rake the leaves second?

Chores

Walk the dog

Do homework

Clean the kitchen

Rake the leaves

There are 4 · 3, or 12, arrangements in

which Nathaniel can complete the chores.

There is one way in which he will walk the

dog first and rake the leaves second. So, the

probability that he will walk the dog first

and rake the leaves second is _ 121.

Lesson 1

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