Simple Events Worksheets Page 3
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indicates multi-step problem
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indicates multi-step problem
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Either Simone will go first or she will not go first. These two events are
complementary events. The sum of the probabilities of an event and its
complement is 1 or 100%. In symbols, P(A) + P(not A) = 1.
Complementary Events
Complement of an Event
Complement of an Event
The probability that event A
3
TALENT COMPETITION
Refer to Example 2. Find the probability that
will not occur is noted as
P(not A ). Since P(A ) +
Simone will not choose the song.
P(not A ) = 1, P(not A )
The probability that Simone will not choose the song is the
= 1 - P(A ). P(not A ) is
read as the probability of
complement of the probability that Simone will choose the song.
the complement of A.
P(A) + P(not A) = 1
Definition of complementary events
_
_
1
1
+ P(not A) = 1
Replace P(A) with
.
6
6
_
_
_
1
1
1
-
-
Subtract
from each side.
6
__________________
6
6
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5
1
6
5
1
P(not A) =
1 -
is
or
-
6
6
6
6
6
_
5
The probability that Simone will not choose the song is
, or about 83%.
6
SCHOOL
Ramón’s teacher uses a spinner similar
1
6
to the one shown at the right to determine the
5
2
order in which each group will make their
presentation. Use the spinner to find each
3
4
probability. Write as a fraction in simplest form.
P(not group 4)
P(not group 1 or group 3)
h.
i.
Use the spinner to find each probability. Write as a
Example 1
T
M
(p. 460)
fraction in simplest form.
S
N
P(M)
P(Q or R)
P(vowel)
1.
2.
3.
R
O
Q
P
P
MARBLES
Robert has a bag that contains 7 blue,
Examples 2, 3
(pp. 461–462)
5 purple, 12 red, and 6 orange marbles. Find
each probability if he draws one marble at random
from the bag. Write as a fraction in simplest form.
P(purple)
P(red or orange)
P(green) 0
4.
5.
6.
P(not blue)
P(not red or orange)
P(not yellow) 1
7.
8.
9.
Number
SURVEYS
Shanté asked her classmates how many
Example 3
10.
Response
of Pets
(p. 462)
pets they own. The responses are in the table. If a
None
6
student in her class is selected at random, what is
1–2
15
the probability that the student does not own 3 or
3 or more
4
more pets?
462
Chapter 9 Probability
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