1. Today we will understand how to add and subtract negative numbers

2. Hole in the sand
Sandcastle -1
+1 or 1
= 0
-1 + (+1) = 0
= 0
+1 + (-1) = 0

3. Adding -2 + -4
= - 6

4. 3 + -3
= 0

5.
= 2

6.
= -1

7. Draw diagrams to explain your answers to these questions
(-5) = 2
= 2 7
(-5) = 1 6 = -1
= -2 -6
= -3 4
(-4 ) = -3 8

8. How many ways can you fill the boxes?
Challenge:
How many ways can you fill the boxes?
Make one box positive and one box negative
= -1
What happens to the answer if you increase the number of sandcastles and holes in the boxes by 1?
Why is this?

9. 5 - 2
5 - 2 = 3

10. -7 - (- 4)
-7 - (- 4) = -3

11. Notice anything interesting?
= -3
Notice anything interesting?
Subtracting -4 is the same as adding 4.

12. Notice anything interesting?
= -3
Notice anything interesting?
Does subtracting -3 give the same answer as adding 3

13. -10 – (-3) = -7 -7 =

14. How can you take away 4 holes that aren’t there???
6 – (- 4) = 10
What addition would give you the same answer?
Why?
6 – (-4)
= 6 + 4
= 10

15. 8 – (- 5) 8 + 5 = 13 -6 – (-2) -6 + 2 = - 4 8 + 10 8 – (-10 ) = 18
For each question write the alternative calculation
8 – (- 5)
8 + 5
= 13
-6 – (-2)
-6 + 2
= - 4
8 + 10
8 – (-10 )
= 18

16. Use diagrams to explain your answers= 6
(-2) = 10 =
-10
(-2 )= -6
3. 2 – 8 = -6
7. -2 – (-8) = 6
4. -2 – 8 =
-10
8. 2 – (-8) = 10
Why do 2 and 4 give the same answer, but not 1 and 3?