3/5+5/20=0.853/6+6/20=0.83/7+7/20=0.7793/8+8/20=0.7753/9+9/20=0.7833/10+10/20=0.8可见3/5+5/20最大,3/8+8/20最小希望能帮到你,祝学习进步O(∩_∩)O