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12.5×0.32×2.5简便计算

12.5×0.32×2.5简便计算 12.5×0.32×2.5 =12.5*0.8*0.4*2.5 =10*1 =10

0.32拆成0.4*0.8 (12.5*0.8)*(0.4*0.25)=10*0.1=1

12.5x0.32x0.5 =12.5x0.8x0.4x0.5 =10x0.2 =2

①12.5×32×2.5=(12.5×8)×(4×2.5)=100×10=1000; ②6.8×9.9=6.8×(10-0.1)=6.8×10-6.8×0.1=68-0.68=67.32;③9.16×2.5-0.5×9.16=9.16×(2.5-0.5)=9.16×2=18.32; ④(1-0.2)÷(1-0.84)=0.8÷0.16=5.

(12.5×8)×(0.04×25) =100×1 =100 原理:把0.32拆开为8乘以0.04,因为12.5乘以8=100能凑成整百,而0.04乘以25也能=整一,说以这样写简便。

12.5*0.8*0.4*0.5=10*0.2=2

25╳0.32╳12.5 =(25×4)×(0.08×12.5) =100×1 =100

用简便方法计算0.4乘2.5乘12.5乘0.8和0.32乘1.25。 0.4乘2.5乘12.5乘0.8和0.32乘1.25。 =(1.25*0.8)*(0.4*2.5)+(1.25*0.8)*0.4 =1*1+0.4 =1.4

0.32X12.5X1.8 =0.04X8X12.5X1.8 =0.04X(8X12.5)X1.8 =0.04X100X1.8 =4X1.8 =7.2

解:原式=25x0.04x8÷12.5 =(25x0.04)x(8÷12.5) =1x0.64 =0.64 分析:主要考察拆分法和结合律的运用。

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