Onmatu- Pre-Algebra Article

Integer numbers II


Let us see first how to subtract integer numbers. Take a look at the following example:
                   - 4 - 2 = - 6.
On a number axis we go from the number - 4 for two position to the left since we have - 2. 
The same goes with the following example:

                  2 - 4 - 3 = - 5.
On a number axis we go from the number 2 for four positions to the left. We come to the number - 2. Next, we go from the number - 2 for three positions to the left. And, we come to our result - 5.

What happens when we take zero (0) into account. Take a look at the following:

                      0 - 5 = - 5.
For your exercise, try with the following:
 
                     -4 - 10 - 7 =

                   - 5 + 27 - 30 =

Multiplication of integer numbers

When we multiply integer numbers, the most important thing to remember is (we will call it "our rule"):
1. + times + is +,

2. + times - is - (- times +) is -,

3. - times - is -.

Now, let us see how our rule works. :)
Take a look at the following examples.

                         - 4 × 2 = 8

                        4 × (- 3) = - 12

                       - 5 × (- 4) = 20

To master multiplication of integer numbers, we need to see what happens with zero (0).

                             2 × 0 = 0

                           0 × (- 4) = 0

Here we can rememeber, let us call it "our rule one":

 Every number multiplied by 0 gives 0.

Good luck! :)

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