Given any 3 digit number you can use the given digits and name another number which is divisible by 37 (e.g. given 628 you say 628371 is divisible by 37 because you know that 6+3 = 2+7 = 8+1 = 9). The question asks you to explain the trick.
The NRICH Project aims to enrich the mathematical experiences of all learners. To support this aim, members of the
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embed rich mathematical tasks into everyday classroom practice.