**Understanding Intervals Across 0** *KS2 Revision*

## What you need to know

**Things to remember:**

- Adding a positive number is like taking away the negative from the positive.
- If we are taking away a big number from a small number, swap them around and put a minus on the answer.

Intervals across 0 just means adding and subtracting so that the numbers swap between positive and negative.

3-8

12-16

-4+8

-2+12

We all know how to add, it is just counting up.

What is 1+4?

So here, we’re starting at 1 and counting up 4 times.

So, 1+4=5!

We do this in the same way when adding a positive number to a negative number.

What is -1+4?

We started at -1 and counted up 4 to get 3, so -1+4=3. But, we also know that 4-1=3. So, we can change the numbers and make it into a subtraction question!

-5+12=12-5=7

-3+9=9-3=6

-10+15=15-10=5

How about if we take a big number away from a small number? What is 4-6?

So, 4-6=-2. It is important to notice that 6-4=2. But why is this important? Let’s put them together to see

4-6=-2

6-4=2

If we swap the numbers we are subtracting, we can see that the answer goes from negative to positive. So, when subtracting a big number from a small number, we can swap them around and just put a negative on the answer!

What is 9-15?

15-9=6

9-15=-6

## Example Questions

**Question 1:** What is -5+8?

-5+8=8-5=3

**Question 2:** What is 7-19?

19-7=12

7-19=-12