解:延長(zhǎng)?$AD，$?交?$BC$?的延長(zhǎng)線于點(diǎn)?$E$?
在?$Rt\triangle ABE$?中，∵?$AB=200m，$??$\angle A=60°$?
∴?$BE=AB·\tan A=200\sqrt {3}m，$??$AE=\frac {AB}{\cos 60°}=400m$?
在?$Rt\triangle CDE$?中，∵?$CD=100m$?
∴?$\angle CED=90°-\angle A=30°$?
∴?$CE=2CD=200m，$??$DE=\frac {CD}{\tan \angle CED}=100\sqrt {3}m$?
∴?$AD=AE-DE=400-100\sqrt {3}m≈227m$?
?$ BC=BE-CE=200\sqrt {3}-200≈146m$?
∴綠地周長(zhǎng)?$=AB+AD+BC+CD=200+227+146+100=673(\mathrm {m})$?
答：綠地周長(zhǎng)是?$673m。$?
