Question

78.9×0.9+7.89x10怎么用简便运算？

Answer 1

78.9×0.9+7.89×10
=7.89×0.9+7.89×10
=7.89×（9+10）
=7.89×19
=7.89×（20-1）
7.89×20-7.89
=7.89×10×2-7.89
=78.9×2-7.89
=157.8-7.89
=149.91

Answer 2

原式=7.89×9+7.89×10=7.89×10-7.89+7.89×10=78.9+78.9-7.89=80-1.1+80-1.1-7.89=80+80-（7.89+1.1+1.1）=160-10.09=149.91

Answer 3

可以把后边部分直接算出来是78.9，整个算式就是78.9乘以1.9，然后用78.9乘以2再减去7.89，也就是789除以5等于157.8减去7.89，也就是150减去0.09等于149.91。

Answer 4

解:原式=7.89ⅹ9+7.89ⅹ10
=7.89ⅹ(10-1)+78.9
=78.9-7.89+78.9
=71.01+78.9
=149.91

Answer 5

将78.9化成7.89x10或将7.89化成78.9x0.1再利用乘法分配律.
原式=7.89x10x0.9+7.89x10
=7.89x(9+10)
=7.89x19
=7.89x(20十1)
=157.8+7.89
=165.69