78.5*46.5-53.5*21.5
问题描述：
78.5*46.5-53.5*21.5
求这道题的简便算法
答
78.5*46.5-53.5*21.5=78.5*46.5-(100-46.5)*(100-78.5)=78.5*46.5-100*100+100*78.5+100*46.5-78.5*46.5=100*(78.5+46.5-100)=2500