作业帮 > 数学 > 作业

在4*7的格子里有几个长方形包括正方形快!

来源:学生作业帮 编辑:作业帮 分类:数学作业 时间:2024/05/21 11:45:45
在4*7的格子里有几个长方形包括正方形快!
正方形 1x1=7x4=28 
            2x2=6x3=18
            3x3=5x2=10
            4x4=4x1=4
       即四种情况(长x宽)相加=60  
  
 长方形 1x2=6x4+3x7=45  { 边长为1x2的长方形=1行的个数x4行+1竖的个数x7竖(如 图),以下分四类,相加=220}
                                                      
              1x3=5x4+2x7=34                              2x3=5x3+2x6=27
             1x4=4x4+1x7=23                               2x4=4x3=1x6=18  
              1x5=3x4+0=12                                   2x5=3x3+0=9
              1x6=2x4+0=8                                     2x6=2x3+0=6
              1x7=1x4+0=4                                     2x7=1x3+0=3
                  
               3x4=4x2+1x5=13                                      4x5=3x1+0=3
               3x5=3x2+0=6                                            4x6=2x1+0=2
               3x6=2x2+0=4                                             4x7=1x1+0=1
               3x7=1x2+0=2  
所以答案是280.
应该是这样.