diff --git a/lib/binary_to_decimal.rb b/lib/binary_to_decimal.rb
index 439e8c6..285162e 100644
--- a/lib/binary_to_decimal.rb
+++ b/lib/binary_to_decimal.rb
@@ -5,5 +5,11 @@
 # 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
+  decimal_sum = 0
+  binary_array.each_with_index do |bit, index|
+    decimal = bit * 2**(binary_array.length - index - 1)
+    decimal_sum = decimal_sum + decimal
+  end
+  return decimal_sum
 end
+
diff --git a/lib/decimal_to_binary.rb b/lib/decimal_to_binary.rb
new file mode 100644
index 0000000..dd9e437
--- /dev/null
+++ b/lib/decimal_to_binary.rb
@@ -0,0 +1,10 @@
+# converts a decimal number received as a parameter into an array of binary digits
+def decimal_to_binary(decimal)
+  binary_array = []
+  until decimal == 0
+    binary_array << decimal % 2
+    decimal = decimal / 2
+  end
+  return binary_array.reverse
+end
+