diff --git a/lib/borrows_many/associations.rb b/lib/borrows_many/associations.rb
index 70e57d9..1ed6c48 100644
--- a/lib/borrows_many/associations.rb
+++ b/lib/borrows_many/associations.rb
@@ -56,7 +56,7 @@ def count(*args)
 
       def calculate(operation, column_name, options = {})
         
-        condtions = options.delete(:conditions)
+        conditions = options.delete(:conditions)
         
         options[:conditions] = "#{@reflection.quoted_link_table_name}.#{@reflection.join_key_name} = #{owner_quoted_id}"
         options[:conditions] << " AND (#{conditions})" if conditions
@@ -66,6 +66,22 @@ def calculate(operation, column_name, options = {})
         super(operation, column_name, options)
       end
 
+      def maximum(*args)
+        calculate(:max, *args)
+      end
+
+      def minimum(*args)
+        calculate(:min, *args)
+      end
+
+      def average(*args)
+        calculate(:avg, *args)
+      end
+
+      def sum(*args)
+        calculate(:sum, *args)
+      end
+
       def construct_sql        
         @finder_sql = "#{@reflection.quoted_link_table_name}.#{@reflection.join_key_name} = #{owner_quoted_id}"
         @finder_sql << " AND (#{conditions})" if conditions
@@ -86,4 +102,4 @@ def construct_join
       end
     end
   end
-end
\ No newline at end of file
+end