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7.5×23+31×2.5的简便运算

7.5x23+31x2.5 =2.5x3x23+31x2.5 =2.5x69+31x2.5 =2.5x(69+31) =2.5x100 =250

奥数基本的要求就是口算功能,上述题目常理按照互乘四位数乘四位数对于小学生可能有些难度,分开吧,换算成(15/2)*23*31*(5/2)再转换(75/4)*((23*30)+(23*1)) ,75改成100-25也可以口算,最后除4,也可以口算。将运算最大控制在2位...

56×23+25×77+31×77 =56x23+(25+31)x77 =56x23+56x77 =56x(23+77) =56x100 =5600

吧相邻两项放在一起,相当于10个1相加

45/31×23+17/31×23-23。用递等式简便运算。 45/31×23+17/31×23-23 =(45/31+17/31-31/31)×23 =1×23 =23

48×23+16×31 =16×3×23+16×31 =16×(3×23+31) =16×100 =1600

14/31×23+17/31×23+23 =23×(14/31+17/31+1) =23×2 =46

8.4×23+31×2.8 =2.8x3x23+31x2.8 =2.8x69+31x2.8 =2.8x(69+31) =2.8x100 =280 希望能帮到你

原式 =(21+39)+(23+37)+(25+35)+(27+33)+(29+31) =60+60+60+60+60 =60x5 =300 或者 =(21+39)x10÷2 =60x10÷2 =60x5 =300 供参考。

=2.31*101-2.31=2.31*(101-1)=2.31*100=231

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