Question

4.5✘3.9✘0.2的简便方法？

Answer 1

=(4.5x0.2)x(4-0.1)
=0.9x(4-0.1)
=3.6-0.09
=3.51
说明一下：最后3.9还是有必要化成4-0.1，因为简便的前提是尽可能只需要口算即可。
以上，供参考。谢谢！

Answer 2

可以先算4.5×0.2，再×3.9，前面等于0.9，然后再乘以3.9，最后结果等于3.51。

Answer 3

4.5x3.9x0.2
=4.5x0.2x3.9
=9x3.9
=（10-1）x3.9
=10x3.9-1x3.9
=39-3.9
=35.1

Answer 4

用乘法交换律，过程如下
4.5×3.9×0.2
=4.5×0.2×3.9
=0.9×3.9
=3.51

Answer 5

4.5×3.9×0.2
=4.5×0.2×3.9
=0.9×3.9
=3.51