小学数学人教版四年级下册教学4单元小数的意义和性质6课时小数点移动引起小数大小的变化

www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com小结：应用小数点移动引起小数大小变化的规律，可以把一个数扩大或缩小。下面各圈里的数同圈上的数比较，有什么变化？探索新知二 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com（1）把0.07分别扩大到原来的10倍、100倍、1000倍，各是多少？0.07×10＝0.07×100＝0.07×1000＝要解决这个问题，怎样列式呢？说一说你是怎么计算的。2探索新知二0.7770 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com小结：把0.7扩大到原来的10倍，就是乘10；把0.7扩大到原来的100倍，就是乘100；把0.7扩大到原来的1000倍，就是乘1000。实际上就是把0.7的小数点分别向右移动一位、两位、三位。探索新知二 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com3.2÷10＝0.323.2÷100＝0.0323.2÷1000＝0.0032（2）把3.2分别缩小到原来的、、，各是多少？100110001101说一说你是怎么计算的。探索新知二 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com小结：把3.2缩小到原来的，就是除以10；把3.2缩小到原来的，就是除以100；把3.2缩小到原来的，就是除以1000。实际上就是把3.2的小数点分别向左移动一位、两位、三位。100110001101探索新知二 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com1.把下面的数分别扩大到原来的10倍、100倍、1000倍。4.80.7354.8×10＝484.8×100＝4804.8×1000＝48000.735×10＝7.350.735×100＝73.50.735×1000＝73512.612.6×10＝12612.6×100＝126012.6×1000＝12600巩固练习三教材做一做翼 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com2.把下面的数分别缩小到原来的、、。93.550093.5÷10＝9.3593.5÷100＝0.93593.5÷1000＝0.09359999÷10＝999.99999÷100＝99.999999÷1000＝9.9991011001100019999500÷10＝50500÷100＝5500÷1000＝0.5巩固练习三教材做一做翼 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com巩固练习三3.教材P46T1