Rob2233 发表于 2017-2-23 21:45 ! O7 k) ^- o! b$ I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; [6 n' z/ b# j' m* I0 t+ y9 D
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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.