diff --git a/zoo.rb b/zoo.rb
new file mode 100644
index 0000000..25241b8
--- /dev/null
+++ b/zoo.rb
@@ -0,0 +1,55 @@
+def sum(x)
+  x.reduce {|x,y| x + y}
+end
+
+class Animal
+  attr_reader :gender
+  def initialize(gender)
+    @gender = gender
+  end
+end
+
+class Zebra < Animal
+  def legs()
+    4
+  end
+  def initialize(gender)
+    super gender
+  end
+end
+
+class Snake < Animal
+  def legs()
+    0
+  end
+  def initialize(gender)
+    super gender
+  end
+end
+
+class Cage
+  attr_accessor :animals
+  def initialize(animals)
+    self.animals = animals
+  end
+end
+
+class Zoo
+  attr_accessor :cages
+  def initialize(cages)
+    self.cages = cages
+  end
+  def animal_count
+    sum(self.cages.map {|x| x.animals.length })
+  end
+  def cage_count
+    self.cages.length
+  end
+end
+
+z = Zoo.new([Cage.new([Zebra.new(:male), Zebra.new(:female), Zebra.new(:male)]),
+             Cage.new([Snake.new(:female), Snake.new(:male), Snake.new(:female), Snake.new(:female), Snake.new(:female)]),
+             Cage.new([Zebra.new(:male), Snake.new(:male)])])
+
+puts z.animal_count.inspect
+puts z.cage_count