Question

(1+0.12+0.23)×（0.12+0.23+0.34）-（1+0.12+0.23+0.34）×（0.12+0.23）用巧算怎么算？

Answer 1

设1+0.12+0.23=a，0.12+0.23+0.34=b
则原式=a*b-(a+0.34)*(b-0.34)
=0.34a-0.34b+0.34*0.34
=0.34*(a-b+0.34)
=0.34*1
=0.34

Answer 2

设0.12+0.23=a
∴(1+0.12+0.23)×（0.12+0.23+0.34）-（1+0.12+0.23+0.34）×（0.12+0.23）
=(1+a)(a+0.34)-(1+a+0.34)×a
=a+a²+0.34+0.34a-a-a²-0.34a
=0.34

Answer 3

(1+0.12+0.23)×（0.12+0.23.0.34）-（1+0.12+0.23+0.34)×（0.12+0.23）
=(0.12+0.23+0.34）+（0.12+0.23)×（0.12+0.23.0.34）-（0.12+0.23）-（0.12+0.23+0.34)×（0.12+0.23）
=（0.12+0.23+0.34）-（0.12+0.23）
=0.34
我们老师讲的...不过我也不太懂就抄上来了.....

Answer 4

(1+0.12+0.23)×（0.12+0.23+0.34）-（1+0.12+0.23+0.34）×（0.12+0.23）
=（0.12+0.23+0.34）+(0.12+0.23)×（0.12+0.23+0.34）-（0.12+0.23）-（0.12+0.23+0.34）×（0.12+0.23）
=0.34