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0.1+0.2+0.3+0.4+……+2.5的简便方法

类似高斯故事里的计算,让我们先观察一下算式,发现可以分组求和,首先为了方便计算可以先提取十分之一,然后再1+25 2+24 3+23 这样分成若干组和为26的算式,最后计算组数发现有12组,再加上落单的13,整理就得到最终结果32.5了,这是等差数列的...

0.1+0.2+0.3+0.4+…+2.5 =(0.1+2.5)x25÷2 =2.6x25÷2 =1.3x25 =32.5

0.1+0.3+0.5+0.7+……+0.99 =(0.1+0.3+...+0.9)+(0.11+0.13+...+0.99) =(0.1+0.9)*5/2+(0.11+0.99)*45/2 =2.5+22.5*1.1 =2.5+24.75 =27.25.

1.2×5.2一2.5÷0.3 =1.2x(5+0.2)-(2.4+0.1)÷0.3 =1.2x5+1.2x0.2-2.4÷0.3-0.1÷0.3 =0.3x4x5+0.24-8-1/3 =0.3x20+0.24-8-1/3 =6+0.24-8-1/3 =-2+0.24-1/3 ≈-2+0.24-0.34 =-2-0.1 =-2.1

(0.1*2*0.3*4*0.5*6*0.7*8*0.9*10*1.1)/(2.2*2.4*2.5*2.7) = 2*3*4*5*6*7*8*9*10*11/22*24*25*27*10*10 (约去2*5=10; 3*9=27,以及11,10) = 4*6*7*8/2*24*25 (约去6*8=2*24) =4*7/25 =28/25

(1.2+0.4)*2.5 =(1+0.2+0.4)*2.5 =(1+0.6)*2.5 =1*2.5+0.6*2.5 =2.5+1.5=4

1、0.4x(2.5-0.25)+2.9 =2.5*0.4-0.4*0.25+2.9 =1-0.1+2.9 =3.9-0.1 =3.8 2、1.25-1.25x0.8 =1.25*(1-0.8) =1.25*0.2 =0.25 3、11.25+11.25x0.8 =11.25*2-11.25*0.2 =22.5-2.25 =20.25 4、(0.25+2.5+25)x0.8 =(0.25+2.5+25)-(0.25+2.5+25...

0.3x2.5 +0.1x2.5 =(0.3 +0.1)x2.5 =0.4x2.5 =1

1÷2.5+2又1/2x0.4+1 =0.4+2.5x0.4+1 =0.4+1+1 =2.4

(1)1.97×0.25×0.4=1.97×(0.25×0.4)=1.97×0.1=0.197;(2)(2.5+0.25)×0.8=2.5×8+0.25×8=20+2=22;(3)3.2×12.5=(4×0.8)×12.5=4×(0.8×12.5)=4×10=40;(4)5.71×8.3-5.71×7.3=5.71×(8.3-7.3)=5.71×1=5.71;(5)0.25×0.44=0.25×(4×...

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