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4.9*5.1+4.9*5.1怎么巧算

解:等差数列和的算法:(首项+末项)×项数÷2 对于这道题即(1+50)×50÷2 =51×25 =1275

5.1×4.5+55×0.51 =0.51×45+55×0.51 =0.51×(45+55) =0.51×100 =51

24x(8-5-1)=24

1+2-3-4+5+6-7-8+9+10-…+2014=2015 观察此式,2-3=-1,-4+5=1,2-3-4+5=0;6-7=-1,-8+9=1,6-7-8+9=0....... =1+(2-3-4+5)+(6-7-8+9)+(10-11-12+13)+...+(2010-2011-2012+2013)+2014 =1+0+0+0+0+0+0+0+...+0+2014 =2015 扩展资料 简便运算方法...

120*4*0.25*0.7 =120*0.7*4*0.25 =84*1 =84 5.1*75-49*7.5-1 =5.1*75-4.9*75-1 =75*(5.1-4.9)-1 =75*0.2-1 =15-1 =14 (20+9.744/2.4)*0.5-1.93 =(20+4.06)*0.5-1.93 =20*0.5+4.06*0.5-1.93 =10+2.03-1.93 =10+0.1 =10.1 不懂可追问,有帮助请...

5.2×9.1+5.2-2.1×5.2 =5.2×(9.1+1-2.1) =5.2×8 =41.6

56×51×4×125 =7×8×51×4×125 =(51×4)×7×(8×125) =204×7×1000 =1428×1000 =1428000

1+2+3+4+5+....+50=1+49+(2+48)+(3+47)+...+(24+26)+25+50=50*25+25=1275

=(1+39)*20/2 =40*10 =400

8.7×3.5+1.3×3.5 =(8.7+1.3)×3.5 =10×3.5 =35

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