4.5*102 257-99 1.8/0.25 12.5*7.2 怎么用简便方法

4.5*102 257-99 1.8/0.25 12.5*7.2 怎么用简便方法

你好,
4.5*102 257-99 1.8/0.25 12.5*7.2
=4.5x(100+2) =257-(100-1) =1.8÷(1÷4) =12.5x8x0.9
=4.5x100+4.5x2 =257-100+1 =1.8÷1x4 =100x0.9
=450+9 =357+1 =1.8x4 =90
=459 =358 =7.2