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有道题:某班有60人。其中42人会游泳,46人会骑车,50人会溜冰,55人会打乒乓球。可以肯定至少有多少人四项都会?(书中的“参考答案”为28人)
There are questions: a class of 60 people. 42 of them will swim, 46 will ride, 50 will skate, and 55 will play table tennis. Can you be sure at least how many people will be four? (The book “reference answer ” to 28 people)