Directed numbers
Adding and subtracting numbers using a number line
We
can use the number line, shown above, to perform simple calculations involving
directed numbers.
Consider solving the mathematical expression below.
-8 + 4 - 3 =
Follow some simple rules.
1) Start at the first number,
as we go left to right, in this case it is -8.
2) Move to the right if the next number is positive(+) or to the left
if it is negative(-). In this case the next number is +4, so we will
move 4 spaces to the right.The next number is -3 so we move 3 spaces
to the left. Follow the animation below.
Keep in mind that if a number is positive we can write it without the + sign in front. For example +8 can be written as simply 8.
In the expression 8 -12 -3 we start on the number line at +8.
Exercise |
Solution |
Answer |
| 1) 8 - 4 + 3 = | ||
| 2) -3 - 4 = | ||
| 3) 3 - 4 - 4 = | ||
| 4) -9 + 6 - 8 = | ||
| 5) 13 - 8 - 9 = | ||
| 6) 19 -23 -11 + 4 = | ||
| 7) 12 - 23 - 4 = | ||
| 8) -10 - 4 -12 = | ||
| 9) -5 + 4 + 3 - 12 = | ||
| 10) -12 + 23 - 14 = |
