9-5: Fundamental Counting Principle 3/31/15

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9-5: Fundamental Counting Principle
3/31/15
What is the
Fundamental Counting Principle
Fundamental
You can use multiplication to find the number of
Counting
possible outcomes in a sample space.
Principle?
If event M has m possible outcomes and event N
has n possible outcomes, then event M followed by
event N has m∙n possible outcomes.
Example 1:
Find the total number of outcomes when choosing
from bike helmets that come in three colors and two
styles.
3 x 2 = 6 outcomes
Example 2:
Two number cubes are rolled. What is the
probability that the sum of the numbers on the cubes
is 12? How likely is it that the sum would be 12?
There is only one outcome where the sum is
12…double 6’s
So… If cube 1 has 6 different possible outcomes
and cube 2 has 6 possible outcomes, then when
you roll the two cubes at once there are 36 possible
outcomes, because 6 x 6 = 36
P(sum of 12) = 1/36, which is unlikely