Year 4 Maths – Counting Backwards Through Zero KS2 Revision
What you need to know
Things to remember:
- Numbers smaller than 0 are called negative numbers
- If we see the “-” symbol before a number we say “minus” that number.
- We can count backwards in negative numbers in the same way we count forwards in positive numbers.
To start a race they will count down, “3, 2, 1, go!” But what would happen if they kept counting down, to 0 and beyond?
A number line would usually look like
When counting up we go to the right, but if are counting down we go to the left. We know that our numbers are getting smaller, but what happens when we go past 0? What is smaller than 0? Negative numbers! A number line with negatives would look like this:
If we look closely, we can see that this number line is the same as the positive one, but the numbers go backwards and have a “-” in front of them. When there is a “-” in front of a number it is called “minus”; they can also be called a negative number.
-12 is minus twelve or negative twelve
-3 is minus three or negative three
Like counting up and down in lots of a number, we can do the same with negative numbers. Let’s take a look.
“Find the next number in the list: 1, 0, -1, -2, __”. The number line tells, us that “-3” comes after “-2”, so that is our answer!
But we might not always be counting down in 1s.
“Find the next number in the list: 4, 2, 0, -2, __”. We know that to get from 4 to 2 we have to subtract 2, so we’re counting down in 2s. The number line shows us that if we count down 2 from “-2” we get “-4”, so that is our answer!
Question 1: Find the next number in the list: -1, -2, -3, -4, __
We can see that we’re counting down by 1 each time, so the next number will be -5.
The answer is -5.
Question 2: Find the next number in the list: 5, 2, -1, -4, __
To get from 5 to 2 we are counting down by 3 each time. If we count down 3 from -4, we get to -7.
The answer is -7.