Theoretical probability
key notes:
The probability is the number of favorable outcomes out of the number of possible outcomes.
Learn with an example
📢 You pick a card at random.

What is P(less than 2)?
Write your answer as a percentage.
______ %
There are 4 cards, numbered 1, 2, 3 and 4. The only number less than 2 is 1. There is 1 number less than 2.
P(less than 2) = 1/4
Write your answer as a decimal. Then convert your answer to a percentage.
1/4 = 0.25 = 25%
P(less than 2) = 25%
📢 You flip a coin.

What is P(heads)?
Flipping a coin has two possibilities: heads or tails.
P(heads) = 1/2
📢 You spin the spinner once.

What is P(2)?
Write your answer as a percentage.
_________ %
The spinner has 4 equal sections, numbered 1, 2, 3 and 4.
P(2) = 1/4
Write your answer as a decimal. Then convert your answer to a percentage.
1/4 = 0.25 = 25%
P(2) = 25%
let’s practice!