1997*0.3+0.5*0.12/1999*0.5
问题描述：
1997*0.3+0.5*0.12/1999*0.5
答
1997×0.3+0.5×0.12÷1995×0.5
=1997×0.3+0.6÷1995×0.5
=1997×0.3＋0.6×0.5÷1995
=1997×0.3＋0.3÷1995
=0.3×（1997+1995分之1）
=0.3×（3984015分之3984015＋3984015分之1997）
=0.3×3984015分之3986012
=0.3×1995分之1996
=6650分之1996
=3325分之988
绝对是我自己做的······