Officially, probability is given as a decimal number between 0 and 1. Probability terms that we learn in Year three and their decimal equivalents are impossible (0), unlikely (0.25), even chance (0.5), likely (0.75) and certain (1).

All probabilities total one as it is certain that something will occur, even if that something is nothing. So the chance of me not having fish and chips tonight + the chance of me not having fish and chips tonight = 1.

If the chance of me having fish and chips was 0.7, then the chances of me not having fish and chips would be 1 - 0.7 = 0.3 (which would be a little more than unlikely).

Probability Questions for GCSE

Twelve questions on probability of the type you might see on a GCSE paper.

Probabilities of a biased spinner

Questions involving knowing that the total of all probabilities is one and applying that knowledge.

Listing combinations video

Listing all possible combinations or permutations of an event helps greatly with calculating individual probabilities.

Experimenting with dice

Investigating possible outcomes for dice throws using experimental methods.

Probability Trees

Simple probability trees to calculate the chances of winning two from three games of monopoly. See the solution video further down the page.

Probability Space Diagram video

A video showing how to set out a probability space diagram and then how to use it to calculate the probability of an event occurring.

Spinner probability video

Video showing you how to calculate the probability of a spinner landing on a particular outcome. Goes through the biased spinner example from the sheet above.

Use a probability tree

Use a probability tree to calculate Anna going to bed on time. Click here to see the solution video.

Probability tree for independent events

Probability tree for independent events

Probability tree for independent events including fractions

Probability tree for independent events including fractions. Click here for the video solution.

Probability tree video

Going throught the breakfast sheet calculating the probabilities making sure each column adds up to one.

Bus probability tree video 2

Probability that Bill is late for his bus is 0.2. What are the chances that...

Probability Spreadsheet

Probability Spreadsheet set up for Key Stage 2 pupils but might be useful for those whom need reminding about the basics. It self marks which is always an advantage.