Adding-and-subtracting-directed-numbers.pptx

Add and subtract

1. Directed numbers Adding and subtracting positive and negative numbers

2. Bath tub? What would happen to a bath if: I added hot water to it? I took the hot water out? I added cold water to it? I took the cold water out? It gets hotter! It gets colder! It gets colder! It gets hotter!

3. Hot and cold numbers… Imagine positive numbers are hot and negative numbers are cold Thinking back to the water analogy, what would happen if: I add a positive number I take away a positive number I add a negative number I take away a negative number It gets hotter! It gets colder! It gets colder! It gets hotter!

4. 3 + 2 Starting point Adding hot = 5

5. -8 + 7 Starting point Adding hot = -1

6. 5 + -3 Starting point Adding cold = 2

7. -4 + -2 Starting point Adding cold = -6

8. 8 - 5 Starting point Taking away hot = 3

9. -3 - 6 Starting point Taking away hot = -9

10. 3 - -4 Starting point Taking away cold = 7

11. -9 - -7 Starting point Taking away cold = -2

12. Your turn! 2 + 7 = -8 + 10 = 7 + -4 = -2 + -5 = 6 – 8 = -4 – 3 = 3 - -5 = -5 - -9 = -6 - -3 = 12 + 5 – 6 + -9 – -4 = 9 2 3 -7 -2 -7 8 4 -3 6