The challenge is to do it using only the digits 1 - 9. ... Carrying introduces an extra 'unstated' digit into the problem, and this is the key to finding a ... So, if we can list all the three digit numbers whose digits sum to 18, then we could work ... Classes from Year 5 up have tried this approach by sharing the work between groups.
arrange-the-digits-1-through-9-into-three-groups
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