199.4*19.93-199.3*19.92的简便计算

199.4×19.93-199.3×19.92
=(199.3+0.1)×19.93-199.3×(19.93-0.01)
=199.3×19.93+19.93×0.1-199.3×19.93+199.3×0.01
=1.993+1.993
=(2-0.007)+(2-0.007)
=4-0.014
=3.986

1.199.4*19.93-199.3*19.92 = = = 2.5.4*3.8-6.5*4.4 2.7*5.4 = = = 12.15和0.87的差乘0.5是多少? (12.15-0.87 )*

把199.4×19.93转换成19.94×199.3，
原式＝19.94×199.3—19.92×199.3
＝（19.94－19.92）×199.3
＝0.02×199.3
＝3.986

199.4x19.93-199.3-19.92
=199.4x19.93-19.93x199.2
=19.93(199.4-199.2)
=19.93x0.2
=3.986