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21x14简便方法计算

原式=21x14/33+14x12/33=21x14/33+14x12x1/33=21x14/33+12x14/33=(21+12)x14/33=33x14/33=14 供参考.

21x19+21x80-99=21x(19+80)-99x1=21x99-99x1=(21-1)x99=20x99=20x(100-1)=20x100-20x1=2000-20=1980

37x14+21x42=37x14+21x14x3=37x14+63x14=(37+63)x14=100x14=1400

=3/14*21/4*16/33约分=3/2*3/4*16/33=9/8*16/33约分=3/1*2/11=6/11

简便方法计算58x21一21x1258x21一21x12=21*(58-12)=21*46=966

34x111+222x33=111*33+111+111*2*33=111*(33+1+66)=111*(33+67)=111*100=11100

144x14一14x14=(144-14)x14=1820

21x19+21x8o-99=21*(19+80)-99=21*99-99=(21-1)*(100-1)=20*100-20=1980 供参考

21X19 =(20+1)(20-1)=400-1=39916X45=2x45x8=90x8=720

(20*1)*30=600+30=630亲,采纳我哟

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