1、第12招 巧算小数加减法 RJ 四年级下册 用简便方法计算：7.136.966.917.22 70.13算式中的四个数都与整数7比较接近，所以将7作为基准数经典例题 70.0470.0970.227.136.966.917.22(70.13)(70.04)(70.09)(70.22)74(0.130.040.090.22)280.2228.22规范解答：13提示：点击进入题组训练运用加法运算律简算运用减法的性质简算运用凑整法简算运用基准数法简算24104.614.61简算。(1)5.264.64.74运用加法运算律简算技 巧 1 5.264.744.6加法交换律(2)2.66.923.40.0
2、8(2.63.4)(6.920.08)6713加法分配律(3)3.242.467.54(4)4.683.020.323.24(2.467.54)3.241013.24加法分配律(4.680.32)3.0253.028.02加法分配律2简算。(1)11.34(7.342.25)11.347.342.25运用减法的性质简算技 巧 2 42.251.75(2)2.37(2.41.63)2.371.632.442.41.62.372.41.63(3)17.8314.763.7617.83(14.763.76)(4)36.2(15.413.8)17.83116.8336.213.815.45015.43
3、4.636.215.413.8运用凑整法简算技 巧 3 3简算。(1)33.2819.4116.6220.5933.2816.62(19.4120.59)33.2816.6219.4120.5949.9409.9(2)3.561.722.44 3.562.441.72 61.724.284简算。(1)9.8810.0210.19.75运用基准数法简算技 巧 4 1040.120.020.10.25(100.12)(100.02)(100.1)(100.25)400.2539.75以10为基准(2)15.414.614.815.315.71550.40.40.20.30.7(100.4)(150.4)(150.2)(150.3)(150.7)750.875.8以15为基准(3)0.90.990.9990.99991111(0.10.010.0010.0001)(10.1)(10.01)(10.001)(10.0001)40.11113.8889以1为基准(4)9.69.79.89.910101010(0.40.30.20.1)(100.4)(100.3)(100.2)(100.1)40139以10为基准
