五年级数学小数乘法的运算定律和简便运算.ppt

,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,*,小数乘法的运算定律 和简便运算,口算下面各题：,0.18.1=0.30.7=720,580=,0.20.34=0.2,0.85=,1.56=,3.041000=,0.40.25=,8.2,1.8=,1.4,0.9=,48016=,2,0.54=,口算下面各题：,0.18.1=,0.81,0.30.7=,0.21,720,580=,140,0.20.34=,0.068,0.2,0.85=,1.05,1.56=,9,3.041000=,3040,0.40.25=,0.1,8.2,1.8=,10,1.4,0.9=,0.5,48016=,30,2,0.54=,1.46,乘法交换律,a,b=b,a,乘法结合律,(,a,b,),c,=,a,(,b,c,),乘法分配律,(,a,b,),c=a,c,b,c,下面每组算式 两边的结果相等吗？,0.8 1.3 1.3 0.8,(0.9 0.4)0.5 0.9 (0.4 0.5),(3.2,2.8)0.6 3.2 0.6,2.8 0.6,整数乘法的运算定律,对小数乘法同样适用。,=,=,=,例,7,用简便方法计算：,（,1,）,0.25 0.73 4,(2)0.32 403,口算下面各题,2.5,0.4=7.3,2.7=1.25 8=,0.21 200=15.7,14.7 =28.6 100=,0.8 1.25 =1.5 6 =0.25 400=,1,10,10,42,1,2860,1,9,100,下面各题怎样算简便就怎样算！,10.4,9.6 0.35 28.6 101,28.6,0.8(4.31.25)(4.23,6.17)0.8,3.12,3.1299 0.8615.7,0.8614.7,=0.81.25 4.3,=3.12,(1,99),=28.6,(101,1),=0.86,(15.7,14.7),我们种了,400,棵向日葵。,平均每棵收葵花籽,0.25,千克。,如果每千克葵花籽可以榨油,0.18,千克，他们收的葵花籽可以榨油多少千克？,解法一：,0.18 0.25 400,解法二：,0.18 (0.25 400),解法二：,0.18 0.25 400,我们种了,400,棵向日葵。,平均每棵收葵花籽,0.25,千克。,如果每千克葵花籽可以榨油,0.18,千克，他们收的葵花籽可以榨油多少千克？,解法一,：,0,.,18,（,0.25 400),五一班开展帮学活动，李明辅导王波学数学。刚学过,小数乘法的简便运算,，课后李明编了一些题目，准备给王波练练。,你们想知道他编的是哪些题目吗？,想一想,2.5,1.7 _,_ 3.6,6.4 _,0.75 _,0.75 _,