7.9╳2.1+2.12的简便方法？

Question

如题所述

Answer 1

7.9×2.1+2.12
=7.9×2+7.9×0.1+2.12
=8×2-0.1×2+0.79+2.12
=16-0.2+0.79+2.12
=15.8+0.79+2.12
=15.8+2.2+0.71
=18+0.71
=18.71
这样计算可以吗，希望你喜欢。

Answer 2

7.9X2.1+2.12
=8X2.1-0.1X2.1+2.12
=16.8+2.12-0.21
=18.92-0.21
=18..71