diff --git a/lib/unit/base.rb b/lib/unit/base.rb
index 50d3dc4..0447e05 100644
--- a/lib/unit/base.rb
+++ b/lib/unit/base.rb
@@ -31,13 +31,7 @@ def +(other)
       if @uom == other.uom
         self.class.new((scalar + other.scalar), @uom, @components + other.components)
       else
-        if self < other
-          scaled_other = other.convert_to(self.uom)
-          self.class.new((@scalar + scaled_other.scalar), scaled_other.uom, @components + other.components)
-        else
-          scaled_self = self.convert_to(other.uom)
-          self.class.new((scaled_self.scalar + other.scalar), scaled_self.uom, @components + other.components)
-        end
+        use_operator_on_other(:+, other)
       end
     end
 
@@ -45,13 +39,7 @@ def -(other)
       if @uom == other.uom
         self.class.new((@scalar - other.scalar), @uom, @components + other.components)
       else
-        if self < other
-          scaled_other = other.convert_to(self.uom)
-          self.class.new((@scalar - scaled_other.scalar), scaled_other.uom, @components + other.components)
-        else
-          scaled_self = self.convert_to(other.uom)
-          self.class.new((scaled_self.scalar - other.scalar), scaled_self.uom, @components + other.components)
-        end
+        use_operator_on_other(:-, other)
       end
     end
 
@@ -147,6 +135,16 @@ def concentration?
       false
     end
 
-    #Display methods
+    private
+
+    def use_operator_on_other(operator, other)
+      if self < other
+        scaled_other = other.convert_to(self.uom)
+        self.class.new((@scalar.send(operator, scaled_other.scalar)), scaled_other.uom, @components + other.components)
+      else
+        scaled_self = self.convert_to(other.uom)
+        self.class.new((scaled_self.scalar.send(operator, other.scalar)), scaled_self.uom, @components + other.components)
+      end
+    end
   end
 end
diff --git a/lib/unit/concentration.rb b/lib/unit/concentration.rb
index 5572fee..ec69cd5 100644
--- a/lib/unit/concentration.rb
+++ b/lib/unit/concentration.rb
@@ -16,32 +16,11 @@ def initialize(numerator, denominator)
     end
 
     def +(other)
-      if other.is_a? Concentration
-        #Add numerators
-        con1, con2 = Concentration.equivalise(self, other)
-        Concentration.new(con1.numerator + con2.numerator,
-                          con1.denominator #This is the same for both cons because of the equivalise method
-                         )
-      elsif other.is_a? Mass
-        Concentration.new(self.numerator + other, self.denominator)
-      elsif other.is_a? Volume
-        #Making the assumption that you're diluting
-        Concentration.new(self.numerator, self.denominator + other)
-      end
+      use_operator_on_other(:+, other)
     end
 
     def -(other)
-      if other.is_a? Concentration
-        con1, con2 = Concentration.equivalise(self, other)
-        Concentration.new(con1.numerator - con2.numerator,
-                          con1.denominator #This is the same for both cons because of the equivalise method
-                         )
-      elsif other.is_a? Mass
-        Concentration.new(self.numerator - other, self.denominator)
-      elsif other.is_a? Volume
-        #Making the assumption that you're diluting
-        Concentration.new(self.numerator, self.denominator - other)
-      end
+      use_operator_on_other(:-, other)
     end
 
     def /(other)
@@ -113,6 +92,21 @@ def unit?
 
     private
 
+    def use_operator_on_other(operator, other)
+      if other.is_a? Concentration
+        #Add numerators
+        con1, con2 = Concentration.equivalise(self, other)
+        Concentration.new(con1.numerator.send(operator, con2.numerator),
+                          con1.denominator #This is the same for both cons because of the equivalise method
+                         )
+      elsif other.is_a? Mass
+        Concentration.new(self.numerator.send(operator, other), self.denominator)
+      elsif other.is_a? Volume
+        #Making the assumption that you're diluting
+        Concentration.new(self.numerator, self.denominator.send(operator, other))
+      end
+    end
+
     def self.equivalise(con1, con2)
       #if equivalent denoms, don't need to convert
       if con1.denominator == con2.denominator
diff --git a/lib/unit/unit.rb b/lib/unit/unit.rb
index 7715520..59c6db4 100644
--- a/lib/unit/unit.rb
+++ b/lib/unit/unit.rb
@@ -11,23 +11,17 @@ def self.scale_hash
     #We need to make sure we can't add different unitless objects together
 
     def +(other)
-      if self.uom != other.uom && other.is_a?(Unit)
-        raise IncompatibleUnitsError.new("You cannot add two different unitless units together")
-      end
+      check_compatibility("add", other)
       super(other)
     end
 
     def -(other)
-      if self.uom != other.uom && other.is_a?(Unit)
-        raise IncompatibleUnitsError.new("You cannot subtract two different unitless units together")
-      end
+      check_compatibility("subtract", other)
       super(other)
     end
 
     def /(other)
-      if self.uom != other.uom && other.is_a?(Unit)
-        raise IncompatibleUnitsError.new("You cannot divide two different unitless units together")
-      end
+      check_compatibility("divide", other)
       if other.is_a?(Volume)
         Concentration.new(self, other)
       else
@@ -36,15 +30,13 @@ def /(other)
     end
 
     def <=>(other)
-      if self.uom != other.uom && other.is_a?(Unit)
-        raise IncompatibleUnitsError.new("You cannot compare two different unitless units together")
-      end
+      check_compatibility("compare", other)
       super(other)
     end
 
     def convert_to(uom)
       if self.uom != uom
-        raise IncompatibleUnitsError.new("You cannot compare two different unitless units together")
+        raise_incompatible_error("compare")
       end
       super(uom)
     end
@@ -52,9 +44,21 @@ def convert_to(uom)
 
     def self.equivalise(u1, u2)
       if u1.uom != u2.uom && other.is_a?(Unit)
-        raise IncompatibleUnitsError.new("You cannot compare two different unitless units together")
+        raise_incompatible_error("compare")
       end
       super(u1, u2)
     end
+
+    private
+
+    def check_compatibility(operation, other)
+      if self.uom != other.uom && other.is_a?(Unit)
+        raise_incompatible_error(operation)
+      end
+    end
+
+    def raise_incompatible_error(operation)
+      raise IncompatibleUnitsError.new("You cannot #{operation} two different unitless units together")
+    end
   end
 end