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這個技巧,組成的四位數一共是4×3×2×1=24個 那麼因為在組成4位數的時候,每個數位機會相等 則每個數位在個位,十比特,百位,千位都出現6次 則和是(2+3+4+5)×(1000+100+10+1)×6=93324
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