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Positive & Negative Positive & Negative Numbers.Numbers.
Adding and Subtracting.Adding and Subtracting.
What’s The Missing Number ?
(1) – 6 + = 12
(2) + 10 = – 3
(3) 12 – = – 22
(4) – 14 = – 25
(5) 22 – = – 17
18
-13
34
-11
39
This is a revision of number facts you already know.
Complete
Some New Rules.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 sum2
The same rule applies for taking away a positive.5 – + 8 = Is the same as 5 – 8 = –3
Subtracting A Negative Subtracting A Negative Number.Number.Five judges have to give a score of between –10 and 10 in a
ball throwing competition.
Here are the judges scores.
– 4 6
– 7 3 – 2
Add up the total score : – 4
The rules say that the lowest score is always removed.
What score is this ? – 7
– 4 6 3 – 2
Now add up the new total:
3
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
Rule 2 : Subtracting a negative is the same as adding the number on.
What a dastardly good rule !!
Some Worked Examples.Some Worked Examples.
Calculate :
( 1) 6 + - 7 = 6 – 7 = -1
( 2) 4 - - 9 = 4 + 9 = 13
( 3) -3 + - 7 = -3 – 7 = -10
( 4) 2 - + 5 = 2 – 5 = -3
( 5) -7 - - 7 = -7 + 7 = 0
What Goes In The Box ?What Goes In The Box ?
( 1) – 5 + – 6 =
(2) 6 + – 4 =
(3) 8 – – 7 =
(4) – 3 – + 8 =
(5) 12 – (– 6 ) =
Is the same as :
– 5 – 6 =
6 – 4 =
8 + 7 =
– 3 – 8 =
12 + 6 =
-11
2
15
-11
18