学生数      

14                                    

13

          12

          11

          10                                         

           9                                         

           8                                           

           7                                         

           6                                           

           5                                         

           4                                              

           3                                            

           2                                               

           1                                                      

                  29  39  49   59   69  79  89   99     成绩