I gave up on that one after finding no non-trivial explanation that made sense to me. I guess in hindsight it makes sense the building material is just given in

I gave up on that one after finding no non-trivial explanation that made sense to me. I guess in hindsight it makes sense the building material is just given in sphere radius, but that didn't click at the time. I couldn't make sense of the 100-m race one either. The only thing I could come up with is maybe the clock freezes/race ends when the first person finishes, and the scores are then done by distance to the finish line.