简便计算：199．4×19．93—199．3×19．92
问题描述：
简便计算：199．4×19．93—199．3×19．92
答
199.4x19.93-199.3x19.92
=199.4x19.93-19.93x199.2
=19.93(199.4-199.2)
=19.93x0.2
=3.986
答
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