The two box-and-whisker plots below show the scores on a math exam for two classes. what do the interquartile ranges tell you about the two classes?

A box-and-whisker plot shows 5 number summary:
 
                                  Class A                Class B
1) minimum value      65                           56
2) 1st quartile            66                            79
3) median                  81                            91
4) 3rd quartile            89                            94
5) maximum value     95                          100

Interquartile range = 3rd Quartile - 1st Quartile 
Class A: 89 - 66 = 23
Class B: 94 - 79 = 15

IQR indicates the spread of the of the scores over the median. Class A has a spread that his more than 50% of the scores of Class B.