4 13 14
It could be number 4, the only square number. Perhaps it's number 13, the only prime number. Or number 14, the number with the most factors. It could be any of them so long as children can justify their thinking. Now try spotting the maverick in this number line-up: 7213, 8547, 3186
What do you think? Might it be 3186 because that's the only even number? Or how about 8547 because 8 x 7 doesn't make 54, whereas 7 x 3 is 21 hence 7213 and 3 x 6 is 18 hence 3186. There are all sorts of creative answers when you start looking.
Try odd one out with shapes too and get children to invent their own for their friends to ponder
John Dabell is a numeracy consultant and teacher trainer