# Probability

Probability was once more prominent in the KS 2 curriculum; now it is only a subsidiary subject which will hardly be studied, especially the harder, mathematical elements. However, knowing the basics may be very useful as a private school in particular has the right to put anything they like on their entrance papers, while probability questions still appear on SATs.

The probability that something will happen is still taught - 'likely, unlikely or impossible' for instance. However, knowing that the chance of two coins ending up on the 'heads' side after being tossed is 0.25 is not something that children tend to learn about.

If you want to work out the probability of an event, look at the number of possible outcomes and the proportion which fulfil the criteria you are looking for. For instance, the chance of a normal dice showing '6' is one out of six, or one sixth. (Or 0.166… if you want to use decimals.)

The chance of the dice showing an ODD number is one out of two, or half, or 0.5, as there are three possible odd numbers (1, 3 and 5) out of the six possible numbers. (Three out of six is the same as one out of two - if this isn't clear then check out the walkthrough on cancelling fractions.)

To work out the chance of a given score, for instance 10, with two dice is more tricky; there are six possible outcomes for each one, meaning there are ( 6 x 6 ) 36 possible outcomes overall. However, there are several ways to make 10.

Dice 1 | Dice 2 |

5 | 5 |

6 | 4 |

4 | 6 |

This means that of the 36 possible outcomes, 3 are going to make a total of 10. The probability of making 10 with two dice is 3 out of 36, or, cancelled down, one twelfth (0.0833…)

While working out probability can be quite intriguing, there's no need to study much more at this age.