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9.9+9.9×99 用简便方法计算

原式=99.9*109.1 =[(99.9+0.1)-0.1]*109.1 =(100-0.1)*109.1 通过加减0.1 使99.9凑出100,化简计算。

0.9+9.9+99.9+999.9 =1-0.1+10-0.1+100-0.1+1000-0.1 =1+10+100+1000-0.1-0.1-0.1-0.1 =1111-0.1×4 =1111-0.4 =1110.6

0.9+9.9+99.9+999.9+9999.9 =(1-0.1)+(10-0.1)+(100-0.1)+(1000-0.1)+(10000-0.1) =(1+10+100+1000+10000)-0.5 =11111-0.5 =11110.5

9.9+9.9×99 =9.9×(1+99) =9.9×100 =990

原式 =(100-1)x9/10 =100x9/10-1x9/10 =90-9/10 =89又1/10 或者 =99x(1-1/10) =99x1-99x1/10 =99-99/10 =99-9又9/10 =89又1/10 供参考。

用简便方法计算 94x(9+99x9) =94×【(1+99)×9】 =94×900 =84600

999又8/9+99又8/9+9又8/9+1/3 =(999又8/9+1/9)+(99又8/9+1/9)+(9又8/9+1/9) =1000+100+10 =1110

9.9+9.9×99 解:简便脱式运算 =9.9x1+9.9x99 运用乘法分配律 =9.9x(1+99) =9.9x100 =990 祝学习进步。

7.9×(99+1)

0.9+9.9+99.9+999.9+9999.9 =1-0.1+10-0.1+100-0.1+1000-0.1+10000-0.1 =(1+10+100+1000+10000)-0.1×5 =11111-0.5 =11110.5

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