Array#in_groups: documentation updated

activesupport/lib/active_support/core_ext/array/grouping.rb

@@ -53,7 +53,7 @@ def in_groups_of(number, fill_with = nil)
   #   ["4", "5"]
   #   ["6", "7"]
   def in_groups(number, fill_with = nil)
-    # size / number gives minor group size;
+    # size.div number gives minor group size;
     # size % number gives how many objects need extra accommodation;
     # each group hold either division or division + 1 items.
     division = size.div number