Every solved figure is a test
In Rule finder, each solved figure turns its outer numbers into the number in the middle by the same rule. Two or three figures are solved for you, and the last one is not.
A rule that fits one figure is only a guess. Try it on the next figure, and the one after that. Keep a rule only if it fits every solved figure, then use it on the last one.
1Pick one rule from the first figure.
2Test it on every other solved figure.
3If one figure breaks it, drop it and try the next rule.
A rule that fits only the first figure
Start with the first figure. Adding all four numbers works: 2 + 4 + 3 + 1 = 10.
Now test it on the second figure: 5 + 1 + 2 + 6 = 14, but the centre is 16. So adding is not the rule.
Try another rule on the first figure: multiply each top number by the number under it, then add. 2 × 3 + 4 × 1 = 10. On the second figure: 5 × 2 + 1 × 6 = 16. It fits both, so that is the rule.
The first figure fits both rules. Only the second one tells them apart, which is why every solved figure has to be checked.
Use the rule that fits both
The last figure has 4 and 3 on top, and 1 and 5 underneath. Use the rule that fits both solved figures, not the one that fits only the first.
Try it
What number goes in the middle of the last figure?
- 19
- 13
Show the answer
19
Right. 4 × 1 + 3 × 5 = 19. Adding all four gives 13, but adding fits only the first figure.
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