Question

78.9×0.9+7.89x10怎么用简便运算？

Answer 1

78.9*0.9+7.89*10
=78.9*0.9+78.9*1
=78.9*1.9=149.91

Answer 2

78.9×0.9+7.89×10
=78.9×（1-0.1）+7.89×10
=78.9-7.89+78.9
=78.9+78.9-7.89
=157.8-7.89
=149.91

Answer 3

78.9×0.9+7.89×10
＝78.9×0.9+78.9×0.1
＝78.9×（0.9+0.1）
＝78.9×1
＝78.9
简便方法：乘法分配律

Answer 4

=（78.9x0.9）+（7.89x10）
=（7.89x9）+（7.89x10）
=7.89x（9+10）
=7.89x19
=149.91

Answer 5

解原式=7.89×9+7.89×10
=7.89×（9+10）
=7.89×19
=149.91