# Revision:Directed numbers

Numbers can either be positive or negative. The name directed number comes from thinking of a number line. The directed part saying which direction from 0 on the number line the number lies: positive numbers being one direction and negative being the other.

Sometimes brackets are put around negative numbers to make them easier to read, e.g. (-2). Other times a '+' or '-' sign is written in front of the number. Both methods are used and you need to be happy using both. If a number is positive, the + is usually missed out before the number. So 3 is really (+3) or +3.

Adding and multiplying combinations of positive and negative numbers can cause confusion and so care must be taken.

• Two 'pluses' make a plus - so if two '+' signs are written next to each other you can replace them with a single '+' sign.
• Thus -3 + (+2) = -3 + 2 = -1
• Two 'minuses' make a plus - so if two '-' signs are written next to each other, you can replace them with a single '+' sign.
• Thus 6 - (-2) = 6 + 2 = 8
• A plus and a minus make a minus - so if one of each sign sit next to each other, then you can replace them with just a '-' sign.
• Thus -4 - (+3) = -4 - 3 = -7 and 3 + (-7) = 3 - 7 = -4

Basically when adding and subtracting directed numbers different signs next to each other mean subtract, the same signs next to each other means add.

## Multiplication and Division

Here there are again three simple rules to follow:

• If two positive numbers are multiplied together or divided, the answer is positive.
• Thus 2 x 4 = 8 and 10 ÷ 2 = 5
• If two negative numbers are multiplied together or divided, the answer is positive.
• Thus (-2) x (-4) = 8 and (-10) ÷ (-2) = 5
• If a positive and a negative number are multiplied or divided, the answer is negative.
• Thus (-2) x 4 = (-8) and 10 ÷ (-2) = (-5)

So basically, when multiplying or dividing two numbers, if your numbers have the same sign the answer is positive, but if the two numbers have different signs the answer is negative.

i think its all right took me awhile to find it though