Probability
Copyright © 2006, Barry Mabillard.
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1.
In a Manitoba school, 10% of the students were born in Saskatchewan, 75% were born
in Manitoba, and the rest were born in Ontario. John decides to run for student president.
The results of the election are as follows:
35% of the students born in Saskatchewan voted for John.
70% of the students born in Manitoba voted for John.
25% of the students born in Ontario voted for John.
a)
What is the probability a student born in Manitoba did not vote for John?
Following the probability tree,
the probability a student born in
Manitoba did NOT vote for John
is 0.225.
b)
If a student voted for John, what is the probability the student was born in Manitoba?
(
)
(
)
(
)
(
)
(
)
P
Manitoba and John
P ManitobaJohn =
P John
0.525
P ManitobaJohn =
0.035+0.525+0.0375
P ManitobaJohn =
0.8787
2.
The probability of rolling a five on a sixsided die is
1
6
. Therefore, the probability of
rolling three consecutive five’s is
1
216
. If a sixsided die is rolled three times, what is the
probability of not rolling three consecutive five’s?
If the probability of rolling three consecutive five’s is
1
216
,
then the complement will give the probability of
not
rolling three consecutive five’s.
The answer is:
1
216
1
1
=

=
216
216 216
215
216
Probability Standards Test ANSWERS
1
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