Here are two fair spinners. The total score is the sum of the two numbers the arrows point to.
Jot down, systematically, all the possible outcomes for the two spinners. You will find it useful to use a table of results, as shown.
|Triangular spinner||Square spinner||Total score|
Use the table to answer these questions:
How many different possible outcomes are there?
12. All you have to do is count the number of entries in the table.
How many outcomes gave a total score of 2?
Only 2 outcomes give a total score of 2: a '1' on each spinner, or a '2' on the triangular spinner and '0' on the square one.
What is the probability of getting a total score of 2?
The number of outcomes giving a total score of 2 ÷ the total number of outcomes = 2/12 or 1/6
What is the probability of getting a total score of 4?
The number of outcomes giving a total score of 4 ÷ the total number of outcomes = 3/12 or 1/4
You can estimate probabilities from an experiment. These are sometimes called experimental probabilities.
For example, in an experiment where you drop a drawing pin:
So the probability of the drawing pin landing up is:
The number of times this outcome occurs (pin up) ÷ total number of outcomes (or trials) = 279/1000 (or 0.279, or 27.9 %).