Counting Principle
Definition of Counting Principle
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Counting principle is used to find the number of possible outcomes.
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Counting principle 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.
Examples of Counting Principle
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Sandra has three skirts S1, S2, and S3 and two T-shirts T1, T2. Then the possible ways she can choose her dress are:
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S1, T1
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S1, T2
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S2, T1
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S2, T2
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S3, T1
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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
Use Counting principle to find the number of outcomes in the given situation.
"3 shirts, 7 skirts and 8 pairs of shoes. How many choices?"
Choices:
A. 168
B. 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, number of outcomes of the situation is 3 × 7 × 8 = 168.
Related Terms for Counting Principle
- Outcomes
- Independent Event
- Permutation
Additional Links for Counting Principle
