Rob2233 发表于 2017-2-23 21:45 * n3 t- I" t" m/ ^8 o如果觉得难度不够的话,可以试试加拿大公开赛(Canadian Open Mathematics Challenge)的题, @, K& B3 F' u! o2 S
这应该是比 ...
& a( e, t: ~5 x1 I1 `thanks a lot as parents, but i guess my daughter going to hate you. i won't let her know who you are. please keep sending this kind good resource for all parents.