第六第六单元单元 小数小数的加法和减法的加法和减法第第4 4课时课时 整数加法运算定律推广到小数整数加法运算定律推广到小数加法交换加法交换加法结合加法结合4.86.38+3.624.7+5.3-2.7+4.3=17.92-(2.38+7.62)=17.92-10=7.92=12.49+(31.84+18.16)=12.49+50=62.49=7.31-2.31-0.3=5-0.3=4.7=(13.64+6.36)+(27.18+12.82)=20+40=607.36+3.64-7.36+3.64=7.36-7.36+3.64+3.64=3.64+3.64=7.2821.48-5.3-4.7 =21.48-(5.3+4.7)=21.48-10=11.480.67+0.85+0.33=1.85(km)100-(55.9+43.1)=1(元)(元)=(1-0.1)+(10-0.1)+(100-0.1)+(1000-0.1)=(1+10+100+1000)-(0.1+0.1+0.1+0.1)=1111-0.4=1110.6=0.1+(1+0.1)+(10+0.1)+(100+0.1)+(1000+0.1)=(1+10+100+1000)+(0.1+0.1+0.1+0.1+0.1)=1111+0.5=1111.5