用递等式计算:(能简便的就用简便方法计算,并写出主要计算过程)(1)38.78-19.59+41.22-30.41(2)2.74×4.86+4.86×6.26+4.86(3)0.08×(12.5+2.5)×0.1(4)25.92+(10.1-14.5×0.2)(5)0.487×12.5÷48.7(6)(8.16+2.09)÷[(10.3-9.3)÷0.4].
(1)38.78-19.59+41.22-30.41, =38.78+41.22-19.59-30.41, =(38.78+41.22)-(19.59+30.41), =80-50, =30; (2)2.74×4.86+4.86×6.26+4.86, =(2.74+6.26+1)×4.86, =10×4.86, =48.6; (3)0.08×(12.5+2.5)×0.1, =(0.08×12.5+0.08×2.5)×0.1, =(1+0.2)×0.1, =1.2×0.1, =0.12; (4)25.92+(10.1-14.5×0.2), =25.92+(10.1-2.9), =25.92+7.2, =33.12; (5)0.487×12.5÷48.7, =0.487÷48.7×12.5, =0.01×12.5, =0.125; (6)(8.16+2.09)÷[(10.3-9.3)÷0.4], =10.25÷[1÷0.4], =10.25÷2.5, =4.1. |