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The product of four different positive integers is 100.
What is the sum of these four integers?
If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.
Make a set of numbers that use all the digits from 1 to 9, once and once only. Add them up. The result is divisible by 9. Add each of the digits in the new number. What is their sum? Now try some other possibilities for yourself!