diff --git a/lib/binary_to_decimal.rb b/lib/binary_to_decimal.rb
index 439e8c6..a80f067 100644
--- a/lib/binary_to_decimal.rb
+++ b/lib/binary_to_decimal.rb
@@ -1,9 +1,20 @@
-# A method named `binary_to_decimal` that receives as input an array of size 8.
-# The array is randomly filled with 0’s and 1’s.
-# The most significant bit is at index 0.
-# The least significant bit is at index 7.
-# 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 = 0
+  binary_array.reverse.each_with_index do |bit, index|
+    unit = bit * 2 ** index
+    decimal += unit
+  end
+  return decimal
+end
+
+def decimal_to_binary(decimal_number)
+  binary_value = []
+  while decimal_number > 0
+    binary_value << (decimal_number % 2)
+    decimal_number = (decimal_number / 2)
+  end
+  until binary_value.length == 8
+    binary_value << 0
+  end
+  return binary_value.reverse
 end
diff --git a/test/binary_to_decimal_test.rb b/test/binary_to_decimal_test.rb
index 18d4bb3..56cf90b 100644
--- a/test/binary_to_decimal_test.rb
+++ b/test/binary_to_decimal_test.rb
@@ -33,3 +33,29 @@
     expect(binary_to_decimal(binary_array)).must_equal expected_decimal
   end
 end
+
+# my tests for decimal_to_binary
+
+describe "decimal to binary" do
+  it "From 162 to 10100010" do
+    decimal = 162
+    expected_binary_array = [1, 0, 1, 0, 0, 0, 1, 0]
+
+    expect(decimal_to_binary(decimal)).must_equal expected_binary_array
+  end
+
+  it "From 26 to 00011010" do
+    decimal = 26
+    expected_binary_array = [0, 0, 0, 1, 1, 0, 1, 0]
+
+    expect(decimal_to_binary(decimal)).must_equal expected_binary_array
+  end
+
+  it "From 207 to 11001111" do
+    decimal = 207
+    expected_binary_array = [1, 1, 0, 0, 1, 1, 1, 1]
+
+    expect(decimal_to_binary(decimal)).must_equal expected_binary_array
+  end
+
+end