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单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,*,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,*,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,*,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,*,R,五年级下册,第,2,课时 稍复杂的找次品问题,R五年级下册第2课时 稍复杂的找次品问题,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,8,个零件里有1个是次品（次品重一些）。假如用天平称，至少称几次能保证找出次品？,新课导入,状元成才路状元成才路状元成才路状元成才路状元成才路状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,“至少称几次就保证,”是什么意思？,是指肯定能找出次品的最少次数。,探究新知,状元成才路状元成才路状元成才路状元成才路状元成才路状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,你们打算怎样表示找次品的过程？,用 表示零件。,状元成才路状元成才路状元成才路状元成才路状元成才路状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,方法一,分成,8,份,重的是次品。,平衡，再各放一个。,状元成才路状元成才路状元成才路状元成才路状元成才路状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,重的是次品。,平衡，再各放一个。,状元成才路状元成才路状元成才路状元成才路状元成才路状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,重的是次品。,平衡，再各放一个。,状元成才路状元成才路状元成才路状元成才路状元成才路状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,重的是次品。,需要称,_,次。,4,状元成才路状元成才路状元成才路状元成才路状元成才路状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,方法二,分成,4,份,再把重的两个分别放到天平的两端。,重的那个就是次品,平衡再放剩下的,4,个。,状元成才路状元成才路状元成才路状元成才路状元成才路状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,再把重的两个分别放到天平的两端。,重的那个就是次品,需要称,_,次。,3,状元成才路状元成才路状元成才路状元成才路状元成才路状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,方法三,分成,3,份,重的那个就是次品,不平衡，重的三个再分出两个各放一边。,平衡，三个中剩下的一个是次品。,状元成才路状元成才路状元成才路状元成才路状元成才路状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,平衡，将剩下的两个一边放一个。,不平衡，重的是次品。,需要称,_,次。,2,状元成才路状元成才路状元成才路状元成才路状元成才路状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,方法四,分成,2,份,重的两个一边放一个,不平衡，将重的四个两个一起放在两边。,不平衡，重的是次品。,需要称,_,次。,3,状元成才路状元成才路状元成才路状元成才路状元成才路状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,将探索的情况填入下表。,状元成才路状元成才路状元成才路状元成才路状元成才路状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,（,1,）表中哪种方法需要称的次数最少？,分成,3,份的时候需要称的次数最少，只需称,2,次。,（,2,）如果,9,个零件中有,1,个次品,(,次品重一些,),，至少称几次能保证找出次品？是怎么称的？,状元成才路状元成才路状元成才路状元成才路状元成才路状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,至少要称,2,次，分成,3,份,1,2,3,4,5,6,7,8,9,1,2,3,4,5,6,平衡,7,8,平衡,9,是次品,不平衡,7,8,7,是次品,状元成才路状元成才路状元成才路状元成才路状元成才路状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,1,2,3,4,5,6,1,2,平衡,3,是次品,1,2,1,是次品,不平衡,不平衡,状元成才路状元成才路状元成才路状元成才路状元成才路状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,（,3,）你能发现什么？用你发现的方法找出,10,个、,11,个零件中的,1,个次品（次品重一些），看看是不是保证找出的次品数也是最少的。,利用天平找次品的时候，把待分的物品,分成,3,份,，能够平均分的平均分成,3,份。,不能平均分的，也应使多的与少的一份,只差,1,。这样不但能保证找出次品，而且称的次数一定最少。,状元成才路状元成才路状元成才路状元成才路状元成才路状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,1.,（,1,）有,8,瓶水，其中有,7,瓶的重量相同，另外有一瓶是糖水，比其他水略重一些，至少称（,）次才能保证找出这瓶糖水。,（,2,）从,9,件物品中找出一件次品（稍轻一些），把,9,件物品分成（,）份较为合适，至少称（,）次就能找到次品。,2,3,2,达标检测,状元成才路状元成才路状元成才路状元成才路状元成才路状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,（,3,）解决找次品的方法很多，在众多的方法中，我们发现分（,）份称的方法最好。,3,状元成才路状元成才路状元成才路状元成才路状元成才路状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,2.1,箱方便面有,7,袋，其中有,6,袋质量相同的，另有一袋质量不足，轻一些，至少称几次才能保证找出这袋方便面？,把,7,袋方便面分成（）份,天平两边各放（）袋。,3,3,状元成才路状元成才路状元成才路状元成才路状元成才路状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,平衡,不平衡,剩下的一定是（）,把轻的一边的,3,袋（）,天平两边各放一袋,平衡,不平衡,剩下的一定是（）,轻的一边是（）,次品,分成,3,份,次品,次品,状元成才路状元成才路状元成才路状元成才路状元成才路状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,有28瓶水，其中27瓶质量相同，另有1瓶是盐水，比其他的水略重一些。至少称几次能保证找出这瓶盐水？,分成,3,份,（,9,，,9,，,10,）,天平两边各放,9,瓶,平 衡,不平 衡,将,10,瓶分成（,3,3,4,）,将重的,9,瓶分成（,3,3,3,）,（一次）,巩固提升,状元成才路状元成才路状元成才路状元成才路状元成才路状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,天平两边各放,3,瓶,天平两边各放,3,瓶,平 衡,不平 衡,将剩下的,3,瓶分成（,1,1,1,）,将重的,3,瓶分成（,1,1,1,）,平 衡,不平 衡,将剩下的,4,瓶分成（,2,2,）,将重的,3,瓶分成（,1,1,1,）,（两次）,状元成才路状元成才路状元成才路状元成才路状元成才路状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,重的是盐水,重的是盐水,天平两边各放,1,瓶,（三次）,（四次）,至少称,4,次。,状元成才路状元成才路状元成才路状元成才路状元成才路状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,课后作业,1.,课本练习二十七，第,2,题、第,5,题；,2.,完成练习册本课时的习题。,状元成才路状元成才路状元成才路状元成才路状元成才路状元成才路,
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