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小数点移动引起小数大小变化的规律,(2),R,四年级下册,一、谈话导入,我们已经学习了小数点的移动的有关知识，你知道小数点,向左,、,向右,移动会引起小数怎样变化吗？,小数点向右,移动一位，小数就扩大到原数的,10,倍；,移动两位，小数就扩大到原数的,(),倍；,移动三位，小数就扩大到原数的,(),倍；,100,1000,（,1,）把,0.07,分别扩大到原数的,10,倍、,100,倍、,1000,倍，各是多少？,0.0710,0.07100,0.071000,说一说你是怎么计算的。,二、探究新知,0.07,扩大到原数的,10,倍,就是乘,10,0.0710,就是把,0.07,的小数点,向右移动一位,0.7,0.07,扩大到原数的,100,倍,就是乘,100,0.07100,就是把,0.07,的小数点,向右移动两位,7,0.07,扩大到原数的,1000,倍,就是乘,1000,0.071000,就是把,0.07,的小数点,向右移动三位,70,把,0.07,扩大到原数的,10,倍，就是,10,；,把,0.07,扩大到原数的,100,倍，就是,100,；,把,0.07,扩大到原数的,1000,倍，就是,1000,。,小,归,纳,结,把一个数扩大到它的,10,倍、,100,倍、,1000,倍,就是把这个数的小数点向右移动一位、两位、三位,小数点移动时，如果位数不够应该怎么办？,小数点移动时，如果位数不够，要用“,0,”补位。,1.,把下面的数分别扩大到原数的,10,倍、,100,倍、,1000,倍。,4.8 0.735 12.6,4.810,48,4.8100,480,4.81000,4800,0.73510,7.35,0.735100,73.5,0.7351000,735,12.610,126,12.6100,1260,12.61000,12600,三、巩固练习,【,选自教材,P44,做一做 第,1,题,】,商品,单价,/,元,数量,10,100,1000,橡皮,2.63,练习本,0.85,直尺,1.63,26.3,263,2630,8.5,85,850,16.3,163,1630,3.,在下表中填出每种商品的总价。,【,选自教材,P45,练习十一 第,2,题,】,43.5,0.435,435,8,0.8,8,670,6.7,0.67,4.,【,选自教材,P45,练习十一 第,3,题,】,48.3,10,4.83,10,(),483,100,100,(),(),0.483,4830,7.29,10,0.729,10,72.9,1000,100,7290,0.0729,5.,填一填。,【,选自教材,P45,练习十一 第,4,题,】,通过今天的学习,，,你都有哪些收获呢,?,四、课堂小结,1.,将下面表格填写完整。,52,850,0.5,备选练习,2.,在方框里填上合适的数。,21.8,0.218,2.18,106,10.6,1.06,390,3.9,0.39,3.,我会计算。,103,0.103,2960,2.96,0.53,53,0.832,0.0832,
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