Definition
The probability of an event is the likelihood of the event occurring.
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Predicting Probability
Independent events ­ when the outcome of one experiment does not affect the outcome of another experiment.
Equally likely outcomes ­ outcomes are equally likely if they have the same probability of occurring.
Ex.
Ex. When tossing a coin and throwing a die, the result of tossing the coin will not affect what number you roll on the die.
When tossing a coin, you are equally likely to toss heads or tails. There is a 50 ­ 50 chance of either.
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Calculating Probability:
Probability = number of favorable outcomes
Total number of outcomes
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Example 1: Suppose a die is rolled.
A) What are the possible outcomes?
C) What is the probability of rolling a 5?
words:
fraction:
B) Are the outcomes equally likely?
ratio:
percent:
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D) What is the probability of rolling an even number?
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E) What is the probability of rolling a number 5 or greater?
words:
words:
fraction:
fraction:
ratio:
ratio:
percent:
percent:
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F) What is the probability of rolling a number less than 3?
words:
fraction:
ratio:
percent:
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Example 2: What is the probability of each event occurring?
A) Drawing a three of hearts
Example 3: In a bag, there are 7 green marbles, 5 red marbles and 10 yellow marbles. What is the probability of pulling out a red marble?
B) Drawing a face card
C) Drawing a spade
D) Drawing a number less than 4
E) Not drawing a face card
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Do pages 282­283
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