Answer for 9/14/17 Review Problem 7.

Note: V, ^, <, and > represent down, up, left, and right arrows,
respectively.
                           75%
Histogram (c)               |  
                        60% V 90%
60 +                     +----+             25 - 20   Q1 - 1
   |            25%      |    |             ------- = ------
50 +             |       |    |             60 - 20   2  - 1
   |         20% V       |    |
40 +           +---------+    |             5 / 40 = (Q1 - 1) / 1
   |           |         |    |
30 +           |         |30% |             0.125 = Q1 - 1
   | 0%        |         |    |   100%
20 + +---------+   40%   |    +----+        median = 1.125
   | |         |         |    |    |
10 + |   20%   |         |    |10% |        75 - 60   Q3  - 2
   | |         |         |    |    |        ------- = -------
 0 + +---------+---------+----+----+        90 - 60   2.5 - 2
     0         1 ^       2  ^      3         
                 |          |               15 / 30 = (Q3 - 2) / 0.5
                 Q1        Q3               
                                            0.5 * 0.5 = Q3 - 2
                                            Q3 = 2.25
                                            
                                            IQR = Q3 - Q1 = 2.25 - 1.125 = 1.125