Probability is how likely an event or series of events will eventually happen. For example, if you flip a coin, there is a 50% chance that it will land on the head side of the coin.

How can probability be expressed?

Probability can be expressed in three ways:

Example questions

Bob flips a coin. The coin has two sides: heads and tails. What is the probability that it will land on heads?

So we know that the coin has two sides, and that the coin can only land on one side. To get the probability, we divide divide the number of times the event we’re looking for could happen (in this case, that’s 1) by the number of possibilities (that’s 2), which gives us ½, 0.5 or 50%.

Jill and her 3 friends are holding a raffle between themselves. Only one person can have their name drawn out of the raffle. What is the probability that Jill’s name will be drawn out of the raffle?

We know that the raffle will have 4 names that can be drawn out of it and that only one person’s name will be drawn out of the raffle. To get the probability, we divide the number of times the event we’re looking for could happen (in this case, that’s 1) by the number of possibilities (that’s 4), which gives us ¼, 0.25 or 25%.

Now you try

Practice questions coming soon.