Crack the number rule
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What you will learn
By the end, you can find the rule of a number sequence (add, subtract, double or square) and work out the next number.
Mila’s secret club changes its door code at every meeting: 3, then 6, then 9, then 12. New members panic and try to memorise the whole list. Mila just smiles. She knows the rule, so she always knows the next code.
Read the explanation
A number sequence follows a rule. To find it, look at the jump between neighbours: 4, 7, 10, 13 jumps by 3 every time, so the rule is add 3. Some sequences double (2, 4, 8, 16), some are square numbers (1, 4, 9, 16) and some use two rules that take turns, like add 5 then subtract 2. Check your rule on every pair before you trust it.
- Find the jump between each pair of numbers.
- Same jump every time? The rule is add or subtract that jump.
- Jumps that grow fast? Try doubling or square numbers.