1. Positive & Negative Numbers. Adding and Subtracting.

2. 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

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 as5 – 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 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

5. Consider the sum below : Old scoreMinus lowest scoreEquals 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) 6 + - 7 =6 – 7 = ( 2) 4 - - 9 =4 + 9 = 13 ( 3) -3 + - 7 =-3 – 7 = -10 ( 4) 2 - + 5 =2 – 5 =-3 ( 5) -7 - - 7 =-7 + 7 = 0

8. 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