The note
How schools teach it now
This uses KS2 arithmetic (adding, taking away, times tables). The 11+ strategy: test a simple rule on the first group (add, take away, multiply), then check it works on the second group before using it on the last one.
5-minute kitchen-table activity
Use playing cards: put down two cards with a number between them that follows a secret rule (4 and 8 with 12 in the middle). Your child guesses the rule and tests it on your next pair. Then swap.
Worked example
7 (15) 2 5 (16) 3 6 ( ? ) 4
- Try adding: 7 + 2 = 9, not 15. Try multiplying: 7 × 2 = 14, one less than 15.
- Test multiply then add 1 on the second group: 5 × 3 + 1 = 16. It works.
- Last group: 6 × 4 + 1 = 25.
Answer: 25
Common mistakes to watch for
- Finding a rule that fits the first group but not testing it on the second.
- Using the numbers in the wrong order for take-away rules.
- Times-table slips in the final step.
Encouragement
- Try saying
- “Try a rule, test it, adjust. That's how mathematicians work.”
- Rather than
- “Just add them, it's always adding.”