Stage: 3 Challenge Level: 
For the Level 3 and 4 problems, start by rearranging the numbers so
that they are in order. Then look at the pairs of
numbers which are closest together.
Properties of numbers. Prime factors. Visualising. Divisibility. Factors and multiples. Multiplication & division. Arithmetic sequence. Workshop. Sequences. Working systematically.
Published November 2009,December 2009.
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