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# How to Add and Subtract Positive and Negative Numbers

## Numbers Can be Positive or Negative:

 Negative Numbers (-) Positive Numbers (+) (This is the Number Line, read about Using The Number Line)

 "-" is the negative sign. "+" is the positive

## No Sign Means Positive

If a number has no sign it usually means that it is a positive number.

Example: 5 is really +5

Example: 2 + 3 = 5 is really saying "Positive 2 plus Positive 3 equals Positive 5".

You could write it as (+2) + (+3) = (+5)

### Subtracting Positive Numbers

This is just simple subtraction.

Example: 6 - 3 = 3 is really saying "Positive 6 minus Positive 3 equals Positive 3".

You could write it as (+6) - (+3) = (+3)

## But what happens if we have negative numbers ... ?

For example, what is 6 - (-3) ?

## Subtracting a Negative is the same as Adding

 Ally can be naughty or nice. So Ally's parents have said "If you are nice we will add 3 points (+3). If you are naughty, we take away 3 points (-3). When you reach 30 Points you get a toy." Ally starts the day with 9 Points:
 Ally's Mum discovers spilt milk: 9-3 = 6 Then Dad confesses he spilt the milk and writes "undo". Mum calculates: 6-(-3) = 6+3 = 9

So if you subtract a negative, you gain points
(ie the same as adding points).

## What About Positive and Negative Together ... ?

It is also possible to have questions like:

What is 6 + (-3) ?
or what is 6 - (+3) ?

They are really the same! Both are subtraction:

## Subtracting a Positive or Adding a Negative is Subtraction

 A few days later. Ally has 12 points. Mum adds 3 points because Ally's room is clean. 12+3 = 15 Dad says "I cleaned that room" and writes "undo" on the chart. Mum calculates: 15 - (+3) = 12 Dad sees Ally brushing the dog. Writes "+3" on the chart. Mum calculates: 12 + (+3) = 15 Ally throws a stone against the window. Dad writes "-3" on the chart. Mum calculates: 15 + (-3) = 12

See: both "15 - (+3)" and "15 + (-3)" result in 12.

It doesn't matter if you subtract positive points or add negative points, you still end up losing points.

## Now, Here Are The Rules

Rule Example +(+) or Two like signs become a positive 3+(+2) = 3+2 = 5 6-(-3) = 6+3 = 9 Two unlike signs become a negative 7+(-2) = 7-2 = 5 8-(+2) = 8-2 = 6

## Try These Exercises ...

Now try This Worksheet, and see how you go.

## ... or Play With It!

 Try playing Casey Runner, you need to know the rules of positive and negative to succeed!