The theoretical probability of a simple event is P(event) =
number of favorable outcomes / total number of outcomes in a sample space
EXAMPLE: A jar contains 10 green, 7 red, and 3 blue marbles. What is the probability of randomly picking a red marble?
P(red) = number of red marbles / total number of marbles in the sample space = 7/10+3 = 7/20
The probability of randomly picking a red marble is 7/20 = 0.35 = 35%
Use the spinner below to complete the problem.
the spinner has the numbers 1, 2, 3, 1, 2, 3, 1, and 2
Determine the probability of the spinner landing on a 3.
Enter the probability as a SIMPLIFIED fraction: __
Enter the probability as a decimal with two decimal places: __
Enter the probability as a percent: __%
Number of favorable outcomes (landing on a 3): 2
Total number of outcomes in the sample space: 8
Probability of landing on a 3 = 2/8 = 1/4 = 0.25 = 25%