Digital sum

Computer Science Level 3

The digital root of a number is obtained by adding together the digits of that number, and repeating that process until a number is arrived at that is less than \(10\).

For example,for \(29953\) the digital root is \(29953 \rightarrow 28\rightarrow 10\rightarrow 1\).

Let \(S\) be the number of all positive integers less than one million that have a digital root of \(1\). What is the digital root of \(S\)?

Check out part 2 for a more challenging version


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