回复：回复：回复：even start with your approach, you should..

1. traverse two sides of the triangle, then 200+400xsqrt(3)=892;
2. traverse three sides of the square, then 100xsqrt(2)+600=714;
3. traverse four sides of the pentagon, then ...

ifi: traverse n-1 sides of n-gon, n=ifinity, then 100+200*pi=728, but this is not feasible by using a compass.

so 714 is good enough