diff --git a/lib/binary_to_decimal.rb b/lib/binary_to_decimal.rb
index 439e8c6..5765d34 100644
--- a/lib/binary_to_decimal.rb
+++ b/lib/binary_to_decimal.rb
@@ -5,5 +5,13 @@
 # Calculate  and return the decimal value for this binary number using
 # the algorithm you devised in class.
 def binary_to_decimal(binary_array)
-  raise NotImplementedError
+  sum = 0
+  exp = binary_array.length - 1
+  binary_array.each do |x|
+    if x == 1
+      sum += 2 ** exp
+    end
+    exp -= 1
+  end
+  return sum
 end
diff --git a/specs/binary_to_decimal_spec.rb b/specs/binary_to_decimal_spec.rb
index ba17713..0cd87bf 100644
--- a/specs/binary_to_decimal_spec.rb
+++ b/specs/binary_to_decimal_spec.rb
@@ -1,6 +1,7 @@
-require 'minitest/autorun'
-require 'minitest/reporters'
-require_relative '../lib/binary_to_decimal'
+
+require "minitest/autorun"
+require "minitest/reporters"
+require_relative "../lib/binary_to_decimal"
 
 describe "binary to decimal" do
   it "From 10011001 to 153" do