Permutations with a twist. Let's go do the twist. And ARCLength!
Difficulty: Are they paying attention? It's a lead-pipe cinch that most will get the degrees of arc and forget to RTFQ.
Standard instructions for this series: No calculator allowed. Express answers in reduced form. Rationalize denominators. Radicals must be reduced. All numbers are base ten unless otherwise specified. Do not approximate radicals or π. Leave such answers as 1025π or √39, for example. Source: UVM Math Contest
answer 18 and answer 24.