What is a number sequence?
A number sequence is a list of numbers that follow a pattern. The numbers may go up or down by the same step each time, such as 2, 4, 6, 8. Once we spot the pattern, we can carry it on and fill in any number that is missing.
Key idea
To find the pattern, work out the step: how much you add or take away to get the next number. Then use the same step again.
Finding the next number
Look at 5, 10, 15, 20. Each time we add 5. So the next number is 20 + 5 = 25. We can check by looking at any two numbers next to each other; the gap is always the same 5.
Worked example
What comes next in 90, 80, 70? The numbers go down by 10 each time. So the next number is 70 − 10 = 60.
Remember
- Find the step first.
- Adding makes the sequence go up.
- Taking away makes it go down.