What is a number sequence?
A number sequence is a list of numbers that follow a rule. The rule tells us how much to add or subtract each time (the step). We use it to find the next number or a missing number.
Key idea
Find the step by looking at two numbers next to each other. Then add the step to count on, or subtract it to count back.
Worked example
2 340, 2 350, 2 360, ___ Each number is 10 more than the one before (the step is +10). So the next number is 2 360 + 10 = 2 370.
Counting on and back
We can count on in 1s, 2s, 5s, 10s, 100s or 1 000s. To count back, we subtract the step. For 3 025, 3 020, 3 015, ___ the step is −5, so the next is 3 010.
Remember
- The step stays the same all through the sequence.
- Adding = counting on; subtracting = counting back.
- Check your answer by using the step again.