7th Grade Math

430 Probability and Predictions

Outcomes occur at random if each outcome occurs by chance. For

example, the number that results when rolling a number cube is a

random outcome.

TALENT COMPETITION Simone and her three friends were deciding

how to pick the song they will sing for their school’s talent show.

They decide to roll a number cube. The person with the lowest

number chooses the song. If her friends rolled a 6, 5, and 2, what

is the probability that Simone will get to choose the song?

The possible outcomes of rolling a number cube are 1, 2, 3, 4, 5,

and 6.

In order for Simone to be able to choose the song, she will need to

roll a 1.

Let P(A) be the probability that Simone chooses the song.

P(A) = ___number of favorable outcomes

number of possible outcomes

= _^16 There are 6 possible outcomes, and 1 of them is favorable.

The probability that Simone will choose the song is _^16 , 0.1

−

6 , or

about 17%.

MUSIC The table shows the numbers New York Philharmonic

Brass Instrument Players

Horn 6

Trombone 4

Trumpet 3

Tuba 1

of brass instrument players in the

New York Philharmonic. Suppose one

brass instrument player is randomly

selected to be a featured performer.

Find the probability of each event.

Write as a fraction in simplest form.

d. P(trumpet) e. P(brass)

f. P(flute) g. P(horn or tuba)

The probability that an event will happen can be any number from

0 to 1, including 0 and 1, as shown on the number line below. Notice

that probabilities can be written as fractions, decimals, or percents.

Impossible

Unlikely

As likely to

happen as not

Likely

Certain

1

4

3

4

1

(^02)
0
0%
0.25
25%
0.5
50%
0.75
75%
1
1
100%
Real-World Link
Founded in 1842, the
New York Philharmonic
is the oldest symphony
orchestra in the
United States. They
have performed over
14,000 concerts.
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