Counting Principle
Definition of Counting Principle
Counting Principle is used to find the number of possible outcomes.
It states that if an event has m possible outcomes and another independent event has n possible outcomes,
then there are mn possible outcomes for the two events together.
Video Examples: The Counting Principle
Example of Counting Principle

Sandra has three skirts S1, S2, and S3 and two Tshirts T1, T2. Then the possible ways she can choose her dress are:
S1, T1
S1, T2
S2, T1
S2, T2
S3, T1
S3, T2
There are 6 distinct possible ways of Sandra choosing her dress. This can easily be calculated using the counting principle as 3 � 2 = 6.
Solved Example on Counting Principle
Ques: Using the counting principle, find the number of possible combinations/choices if there are 3 shirts, 7 skirts and 8 pairs of shoes.
Choices:
A. 168B. 18
C. 80
D. 45
Correct Answer: A
Solution:

Step 1: Number of outcomes of picking a shirt from 3 shirts is 3.
Step 2: Number of outcomes of picking a skirt from 7 skirts is 7.
Step 3: Number of outcomes of picking a pair of shoes from 8 pairs is 8.
Step 4: So, the number of possible combinations/choices in the given situation is 3 � 7 � 8 = 168.
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