用简便方法计算下面的题:12.5✘8.7,2.5✘4.4-2.5✘0.4，5.24+5.24✘99

解，12.5x8.7
=12.5x(8+0.8-0.1)
=12.5x8+12.5x0.8-12.5x0.1
=100+10-1.25
=108.75
2.5x4.4-2.5x0.4
=2.5x(4.4-0.4)
=2.5x4
=10
5.24+5.24x99
=5.24x(1+99)
=5.24x100
=524

(1)12.5×8.7 (根据125×8＝1000)
=12.5×(8+0.8-0.1)
=100+10-1.25
=109.75
(2)2.5×4.4-2.5×0.4 (逆用乘法分配律)
=2.5×(4.4-0.4)
=2.5×4
=10
(3)5.24+5.24×99 (逆用乘法分配律)
=5.24×(1+99)
=5.24×100
=524本回答被网友采纳

12.5X8.7
=12.5Ⅹ8+12.5X0.7
=100+8.75
=108.75

2.5X4.4-2.5X0.4
=2.5X(4.4-0.4)
=2.5X4
=10

5.24+5.24X99
=5.24X(1+99)
=5.24X100
=524

12.5x8.7=12.5x(8+0.8-0.1)=12.5x8+12.5x0.8-12.5x0.1=108.75
2.5x4.4-2.5x0.4=2.5x（4.4-0.4）=10
5.24+5.24x99=5.24x（1+99）=524