Positive

1
Positive Negative Numbers.

• Adding and Subtracting.

2
Whats The Missing Number ?
This is a revision of number facts you already
know.
Complete
(1) 6 12
18
(2) 10 3
-13
(3) 12 22
34
(4) 14 25
-11
(5) 22 17
39
3
Some New Rules.
What happens if you add a negative number ?
Consider the sum below
6

4

Rule 1 Adding a negative number is just the
same as taking away that number. Hence
6
4

Is the same sum
2
The same rule applies for taking away a positive.
5 8
Is the same as
5 8
3
4
Subtracting A Negative Number.
Five judges have to give a score of between 10
and 10 in a ball throwing competition.
Here are the judges scores.
4
7
3
2
6
4
Add up the total score
The rules say that the lowest score is always
removed.
What score is this ?
7
Now add up the new total
6
3
4
3
2
5
Consider the sum below
Old score
Minus lowest score
Equals new score.
Put the numbers in place of the statements
4

7
3

That is to say
4 ( 7 ) 3
Which is the same as
4 7 3
6
Rule 2 Subtracting a negative is the same as
adding the number on.
What a dastardly good rule !!
7
Some Worked Examples.
Calculate
-1
( 1) 6 - 7
6 7
13
( 2) 4 - - 9
4 9
-10
( 3) -3 - 7
-3 7
( 4) 2 - 5
2 5
-3
0
( 5) -7 - - 7
-7 7
8
What Goes In The Box ?
Is the same as
5 6
-11
( 1) 5 6
6 4
2
(2) 6 4
8 7
15
(3) 8 7
3 8
-11
(4) 3 8
12 6
18
(5) 12 ( 6 )