2520 is the smallest number that can be divided by each of the numbers from 1 to 10 without any remainder.
What is the smallest positive number that is evenly divisible by all of the numbers from 1 to 20?
This seems like a job for a function that finds the least common
multiple of two values and then using the .fold method on
ranges.
...
And indeed it was, modulo a few quirks of rust that I'm still learning (like forgetting to specify function return values each time).