# 0 12345678910-10-9-8-7-6-5-4-3-2 When we add or subtract integers we can use a number line to help us see what is happening with the numbers.

## Presentation on theme: "0 12345678910-10-9-8-7-6-5-4-3-2 When we add or subtract integers we can use a number line to help us see what is happening with the numbers."— Presentation transcript:

0 12345678910-10-9-8-7-6-5-4-3-2 When we add or subtract integers we can use a number line to help us see what is happening with the numbers.

0 12345678910-10-9-8-7-6-5-4-3-2 At the centre of the number line is the integer zero.

0 12345678910-10-9-8-7-6-5-4-3-2 The positive numbers are to the right along the number line. When we add integers we move “up” in this direction.

0 12345678910-10-9-8-7-6-5-4-3-2 The negative numbers are to the left along the number line. When we subtract integers we move “down” in this direction.

0 12345678910-10-9-8-7-6-5-4-3-2 Example: 1 + 3 = ?

0 12345678910-10-9-8-7-6-5-4-3-2 Example: 1 + 3 = ? Let’s start at the first integer in our sum, that is, positive one.

0 12345678910-10-9-8-7-6-5-4-3-2 Example: 1 + 3 = ? Let’s start at the first integer in our sum, that is, positive one.

0 12345678910-10-9-8-7-6-5-4-3-2 Example: 1 + 3 = ? Let’s start at the first integer in our sum, that is, positive one. We are going to add +3 so we need to move 3 places up (to the Right on our number line).

0 12345678910-10-9-8-7-6-5-4-3-2 Example: 1 + 3 = ? Let’s start at the first integer in our sum, that is, positive one. We are going to add +3 so we need to move 3 places up (to the Right on our number line).

0 12345678910-10-9-8-7-6-5-4-3-2 Example: 1 + 3 = ? Let’s start at the first integer in our sum, that is, positive one. We are going to add +3 so we need to move 3 places up (to the Right on our number line). +1

0 12345678910-10-9-8-7-6-5-4-3-2 Example: 1 + 3 = ? Let’s start at the first integer in our sum, that is, positive one. We are going to add +3 so we need to move 3 places up (to the Right on our number line). +2

0 12345678910-10-9-8-7-6-5-4-3-2 Example: 1 + 3 = ? Let’s start at the first integer in our sum, that is, positive one. We are going to add +3 so we need to move 3 places up (to the Right on our number line). +2

0 12345678910-10-9-8-7-6-5-4-3-2 Example: 1 + 3 = ? Let’s start at the first integer in our sum, that is, positive one. We are going to add +3 so we need to move 3 places up (to the Right on our number line). +2

0 12345678910-10-9-8-7-6-5-4-3-2 Example: 1 + 3 = ? Let’s start at the first integer in our sum, that is, positive one. We are going to add +3 so we need to move 3 places up (to the Right on our number line). +3

0 12345678910-10-9-8-7-6-5-4-3-2 Example: 1 + 3 = ? Let’s start at the first integer in our sum, that is, positive one. We are going to add +3 so we need to move 3 places up (to the Right on our number line). +3 We end up at the value 4. So… 1 + 3 = 4

0 12345678910-10-9-8-7-6-5-4-3-2 Example: 1 + 3 = 4

0 12345678910-10-9-8-7-6-5-4-3-2 Example: 1 - 3 = ?

0 12345678910-10-9-8-7-6-5-4-3-2 Example: 1 - 3 = ? We will start at +1 again as this is the first part of our sum

0 12345678910-10-9-8-7-6-5-4-3-2 Example: 1 - 3 = ? This time we are subtracting 3 so we will move “down” (to the left) on our number line

0 12345678910-10-9-8-7-6-5-4-3-2 Example: 1 - 3 = ? This time we are subtracting 3 so we will move “down” (to the left) on our number line

0 12345678910-10-9-8-7-6-5-4-3-2 Example: 1 - 3 = ? This time we are subtracting 3 so we will move “down” (to the left) on our number line

0 12345678910-10-9-8-7-6-5-4-3-2 Example: 1 - 3 = ? This time we are subtracting 3 so we will move “down” (to the left) on our number line

0 12345678910-10-9-8-7-6-5-4-3-2 Example: 1 - 3 = ? This time we are subtracting 3 so we will move “down” (to the left) on our number line -2

0 12345678910-10-9-8-7-6-5-4-3-2 Example: 1 - 3 = ? This time we are subtracting 3 so we will move “down” (to the left) on our number line -2

0 12345678910-10-9-8-7-6-5-4-3-2 Example: 1 - 3 = ? This time we are subtracting 3 so we will move “down” (to the left) on our number line -3

0 12345678910-10-9-8-7-6-5-4-3-2 Example: 1 - 3 = ? -3 We end up at negative two. So… 1 – 3 = -2

0 12345678910-10-9-8-7-6-5-4-3-2 Example: 1 - 3 = -2

0 12345678910-10-9-8-7-6-5-4-3-2 What about: -4 - 3 = ?

0 12345678910-10-9-8-7-6-5-4-3-2 What about: -4 - 3 = ? We will start at negative four on the number line

0 12345678910-10-9-8-7-6-5-4-3-2 What about: -4 - 3 = ? We are subtracting 3 so we will move “down” (to the left) on our number line by 3 units

0 12345678910-10-9-8-7-6-5-4-3-2 What about: -4 - 3 = ? We are subtracting 3 so we will move “down” (to the left) on our number line by 3 units

0 12345678910-10-9-8-7-6-5-4-3-2 What about: -4 - 3 = ?

0 12345678910-10-9-8-7-6-5-4-3-2 What about: -4 - 3 = ?

0 12345678910-10-9-8-7-6-5-4-3-2 What about: -4 - 3 = ?

0 12345678910-10-9-8-7-6-5-4-3-2 What about: -4 - 3 = ?

0 12345678910-10-9-8-7-6-5-4-3-2 What about: -4 - 3 = ?

0 12345678910-10-9-8-7-6-5-4-3-2 What about: -4 - 3 = ? We end up at negative seven, so…

0 12345678910-10-9-8-7-6-5-4-3-2 What about: -4 - 3 = -7

0 12345678910-10-9-8-7-6-5-4-3-2 Finally, what do these mean? 5 + -2 ? 5 - -2 ?

0 12345678910-10-9-8-7-6-5-4-3-2 Finally, what do these mean? 5 + -2 ? 5 - -2 ? A plus and minus together means the same as subtract. So replace them with a minus sign

0 12345678910-10-9-8-7-6-5-4-3-2 Finally, what do these mean? 5 + -2 is the same as 5 - 2 5 - -2 ? A plus and minus together means the same as subtract. So replace them with a minus sign

0 12345678910-10-9-8-7-6-5-4-3-2 Finally, what do these mean? 5 + -2 is the same as 5 - 2 5 - -2 ? Two minus signs together means the same as add. So replace them with a plus sign

0 12345678910-10-9-8-7-6-5-4-3-2 Finally, what do these mean? 5 + -2 is the same as 5 - 2 5 - -2 is the same as 5 + 2

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