diff --git a/lib/.DS_Store b/lib/.DS_Store
new file mode 100644
index 0000000..707d654
Binary files /dev/null and b/lib/.DS_Store differ
diff --git a/lib/core_extensions/array.rb b/lib/core_extensions/array.rb
index c726d5f..3e6e6cb 100644
--- a/lib/core_extensions/array.rb
+++ b/lib/core_extensions/array.rb
@@ -2,9 +2,10 @@ class Array
   def entropy
     each_with_object(Hash.new(0)) do |i, result|
       result[i] += 1
-    end.values.inject(0) do |sum, count|
+    end.values.sum do |count|
       percentage = count.to_f / length
-      sum + -percentage * Math.log2(percentage)
+
+      -percentage * Math.log2(percentage)
     end
   end
 end
diff --git a/lib/decisiontree/id3_tree.rb b/lib/decisiontree/id3_tree.rb
index 9434299..9097ebf 100755
--- a/lib/decisiontree/id3_tree.rb
+++ b/lib/decisiontree/id3_tree.rb
@@ -120,12 +120,12 @@ module DecisionTree
       index = attributes.index(attribute)
 
       values = data.map { |row| row[index] }.uniq
-      remainder = values.sort.inject(0) do |sum, val|
+      remainder = values.sort.sum do |val|
         classification = data.each_with_object([]) do |row, result|
           result << row.last if row[index] == val
         end
 
-        sum + ((classification.size.to_f / data.size) * classification.entropy)
+        ((classification.size.to_f / data.size) * classification.entropy)
       end
 
       [data.classification.entropy - remainder, index]