摘要：小颖和小红两位同学在学习“概率 时.做投掷骰子实验.他们共做了60次实验.实验的结果如下: 朝上的点数 1 2 3 4 5 6 出现的次数 7 9 6 8 20 10 (1)计算“3点朝上 的频率和“5点朝上 的频率． (2)小颖说:“根据实验.一次实验中出现5点朝上的概率最大 ,小红说:“如果投掷600次.那么出现6点朝上的次数正好是100次． 小颖和小红的说法正确吗?为什么? (3)小颖和小红各投掷一枚骰子.用列表或画树状图的方法求出两枚骰子朝上的点数之和为3的倍数的概率． 解:(1)“3点朝上 出现的频率是······························································ 2分 “5点朝上 出现的频率是················································································ 4分 (2)小颖的说法是错误的．这是因为.“5点朝上 的频率最大并不能说明“5点朝上 这一事件发生的频率最大．只有当实验的次数足够大时.该事件发生的频率稳定在事件发生的概率附近．························· 2分 小红的判断是错误的.因为事件发生具有随机性.故“6点朝上 的次数不一定是100次． ·················································································································· 4分 (3)列表如下: 1 2 3 4 5 6 1 2 3 4 5 6 7 2 3 4 5 6 7 8 3 4 5 6 7 8 9 4 5 6 7 8 9 10 5 6 7 8 9 10 11 6 7 8 9 10 11 12 ············································································· 2分 ·················································································· 4分

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