# Maths Topics

Guide for an end of year exam, you will need to anotate

- Created by: Rachel
- Created on: 26-04-11 17:36

First 251 words of the document:

Revision for maths

Negative Numbers

Multiplication and division

Positive ×/ positive = positive

Positive ×/ negative = negative

Negative ×/ positive = negative

Negative ×/ negative = positive

Adding Negative Numbers

If I walk 3 steps forward and then 5 steps forward, it's the same as if I walked 8 steps

forward, because:

If I walk 3 steps forward and then 5 steps backward, I'll end up 2 steps behind where I

started, i.e., as if I walked 2 steps backward. To describe this example as an addition, I need

to describe all my walking in terms of steps forward. So I can say that if I walk 3 steps

forward and then -5 steps forward, it's the same as if I had walked -2 steps forward,

because:

Subtracting Negative Numbers

If I walk 9 steps forward and then 6 steps backward, it's the same as if I had walked 3 steps

forward, because:

If I walk 9 steps forward and then 6 steps forward, it's the same as if I has walked 15 steps

forward. To turn that into a subtraction problem, I have to describe the 6 steps forward as -6

steps backward. That is, if I walk 9 steps forward and then -6 steps backward, it's the same

as if I had walked 15 steps forward, because:

Multiplying Negative Numbers

If I walk 3 steps forward 5 times, then in total I will have walked 15 steps forward. This

corresponds to the multiplication:

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