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 T-shirts T1, T2. Then the possible ways she can choose her dress are:
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.
Correct Answer: A
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.