3.6×1994.4+2006.9×6.4要巧算

分类: 作业答案 • 2021-12-18 22:44:06

问题描述：

3.6×1994.4+2006.9×6.4
要巧算

答

=10*1994.4-6.4*1994.4+2006.9*6.4
=19944+6.4*(2006.9-1994.4)
=19944+6.4*12.5
=19944+6.4*100÷8
=19944+80
=20024

答

3.6×1994.4+2006.9×6.4
=3.6×1994.4+(1994.4+12.5)×6.4
=3.6×1994.4+1994.4×6.4+12.5×6.4
=1994.4×（3.6+6.4）+12.5×8×0.8
=19944+80
=20024