Rob2233 发表于 2017-2-23 21:45% n5 W! P% y' y
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,7 T" P: z' N, E% T
这应该是比 ...
' D4 N/ G7 x- X9 s) B j. D! fthanks 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.