Added an example of finite arithmetic problems.

diff --git a/testing/RealWorld.md b/testing/RealWorld.md
index d9bbce7660158bac3a356858a49ef63d9a8ef41d..16dd0632be8ae0d91c10891f6026e4cb8b3644ef 100755 (executable)
--- a/testing/RealWorld.md
+++ b/testing/RealWorld.md
@@ -14,7 +14,17 @@ The [Muon Ion Cooling Experiment](http://www.mice.iit.edu/) (MICE) have a large
 
 ## When 1 + 1 = 2.0000001
 
-Computers don't do floating point arithmetic too well. This can make simple tests for the equality of two floating point values problematic due to imprecision in the values being compared. 
+Computers don't do floating point arithmetic too well.  For example:
+
+    $ python
+    >>> tot = 0.0\r
+    >>> for i in range(1,100):\r
+    >>>...  tot = tot + 0.01 # Expect answer to be 1.0\r
+    >>>...\r
+    >>> print tot\r
+    >>> 0.99\r
+
+This can make simple tests for the equality of two floating point values problematic due to imprecision in the values being compared. 
 
     $ python
     >>> expected = 1 + 1