Numbers

Directed Numbers

Many of the numbers we use represent situations which have directions as well as size
The numbers which have a direction and a size are called directed numbers.
Once a direction is chosen as positive (+), the opposite direction is taken as negative (- ).
For example:
If above zero degrees is positive (+), then below zero degrees is negative.
If north is positive (+), then south is negative (-).
If profit is positive (+), then loss is negative (-).
Directed numbers are used in Mathematics, Engineering, Business and the Sciences.
For example: -15,  8,  100,  -100,  -3.5,  0.33,  -0.75   are directed numbers.
In the above example -15,  8,  100, -100 are called integers.
When writing positive numbers you can leave the positive sign and just write the number.
eg. +8  as  8

If  a directed number is a whole number, it is called an integer.

Example

Addition of Directed Numbers

Let's consider   -3  + + 4

In this problem  + and +  signs are side by side.There is no number in between them. So the two positive signs which are side by side gives a positive sign.

Remember this,

                             Two like signs give a positive sign

                                               + +  =  +

                            -3  + + 4  =  - 3  +  4

                                            =    1

Sometimes directed numbers are written as