The theoretical probability of a simple event is P(event) = number of favorable outcomestotal 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 marblestotal number of marbles in the sample space=710+7+3=720
The probability of randomly picking a red marble is
720=0.35=35%
Use the spinner below to complete the problem.
Determine the probability of the spinner landing on a 3.
(3 points)
To determine the probability of the spinner landing on a 3, we need to count the number of favorable outcomes (which is 1, since there is only one 3 on the spinner) and divide it by the total number of outcomes on the spinner (which is 8, since there are 8 equal sections on the spinner).
P(landing on a 3) = number of 3's on the spinner total number of sections on the spinner
P(landing on a 3) = 1/8
P(landing on a 3) = 0.125 or 12.5%
Therefore, the probability of the spinner landing on a 3 is 0.125 or 12.5%.