05/31/2020 (2011: National Sprint Round, Problem 1)

Q: What is the sum of all of the two-digit positive integers "AB" with the property that the units digit, B, is four times the tens digit, A?

A: 42
The smallest number to have a units digit that is four times the tens digit is 14. We find the next number which satisfies this, which is 28. 14 + 28 = 42

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