Divisibility rules
Seven tests a child can run in their head, so "does 4 go into this?" stops being a long-division problem. Each one comes with a number it is happening to.
Reference chart
Divisibility rules
Look at the last digit
- 2346ends even
- 5245ends 0 or 5
- 10870ends 0
Add up the digits
- 35,1245 + 1 + 2 + 4 = 1212 = 3 × 4
- 94,7614 + 7 + 6 + 1 = 1818 = 9 × 2
Two steps
- 41,31616 = 4 × 4
- 6138even, and 1 + 3 + 8 = 12passes 2 and 3
What's on this chart
A divisibility rule is a shortcut with a real payoff: it turns a division a child would have to work out into something they can see. Faced with 5,124, a child either sets up a division or adds 5+1+2+4, gets 12, and knows immediately that 3 divides it. The second child has more attention left over for the actual question.
Why this chart helps
The rules are grouped here by what the test asks you to do rather than by the size of the number, because that grouping is the lesson. Nearly every rule a primary child needs is either look at the end or add up the digits, and seeing them sorted that way is what makes seven separate facts into two ideas with a couple of extras.
More printable charts
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