四年级下册数学小数加减法四大简算方法


简介:
一、运用加法运算律简算 1.5.26+4.6+4.74 =5.26+4.74+4.6 =10+4.6 =14.6 (加法交换律) 2.2.6+6.92+3.4+0.08 =(2.6+3.4)+(6.92+0.08) =6+7 =13 (加法分配律) 二、运用减法的性质简算 3.11.34-(7.34+2.25) =11.34-7.34-2.25 =4-2.25 =1.75 4.2.37-(2.4-1.63) =2.37-2.4+1.63 =2.37+1.63-2.4 =4-2.4 =1.6 三、运用凑整法简算 5.33.28-19.41+16.62-20.59 =33.28+16.62-19.41-20.59 =33.28+16.62-(19.41+20.59) =49.9-40 =9.9 6.3.56-1.72+2.44 =3.56+2.44-1.72 =6-1.72 =4.28 四、运用基准数法简算 7.7.0.9+0.99+0.999+0.9999 =(1-0.1)+(1-0.01)+(1-0.001)+(1-0.0001) =1+1+1+1-(0.1+0.01+0.001+0.0001) =4-0.1111 =3.8889 (以1为基准) 8.9.6+9.7+9.8+9.9 =(10-0.4)+(10-0.3)+(10-0.2)+(10-0.1) =10+10+10+10-(0.4+0.3+0.2+0.1) =40-1 =39 (以10为基准)