用简便算法解答2道数学题

问题描述:

用简便算法解答2道数学题
12.7*3.1-1.27
7.98*1.7+79.8*0.33

1,=12.7(3+0.1)-1.27
=38.1+1.27-1.27
=38.1
2,=7.98*(1.7+3.3)
=7.98*5
=39.9