3.8×9.9＋0.38如何简便计算?今晚用 请快些

3.8×9.9＋0.38=0.38(10×9.9+1)=0.38×(99+1)=0.38×100=38

需要把0.38转换成3.8乘以0.1就行了！

3.8×9.9＋0.38=3.8×9.9+3.8×0.1=3.8×（9.9+0.1）=38

3.8（9.9+0.1）=3.8×10=38

=3.8x(10-0.1)+0.38
=3.8x10+0.38-1x0.38
=38+0
38

3.8×9.9＋0.38
=0.38x(99+1)
=0.38x100
=38