# Maths

Maths

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## Surds

• A surd is a square root which cannot be reduced to a whole number. For example, is not a surd, as the answer is a whole number. But is not a whole number. You could use a calculator to find that but instead of this we often leave our answers in the square root form, as a surd.
• You need to be able to simplify expressions involving surds. Here are some general rules that you will need to learn.
•  If you are adding the square root of a to b it is not the square root of a+b.

e.g.

Simplify

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## Probability and tree diagrams

Tree diagrams allow us to see all the possible outcomes of an event and calculate their probability. Each branch in a tree diagram represents a possible outcome.

If two events are independent, the outcome of one has no effect on the outcome of the other. For example, if we toss two coins, getting heads with the first coin will not affect the probability of getting heads with the second.

A tree diagram which represent a coin being tossed three looks like this :

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