diff --git a/heikin.rb b/heikin.rb
new file mode 100755
index 0000000..746adfc
--- /dev/null
+++ b/heikin.rb
@@ -0,0 +1,9 @@
+#!/usr/bin/env ruby
+# -*-coding: utf-8 -*-
+
+def heikin (x, y, z)
+  wa = x + y + z
+  return wa/3
+end
+
+puts heikin(3, 4, 2)
diff --git a/hello2.rb b/hello2.rb
new file mode 100755
index 0000000..a4bf225
--- /dev/null
+++ b/hello2.rb
@@ -0,0 +1,11 @@
+#!/usr/bin/env ruby
+# -*-coding: utf-8 -*-
+
+def hello2(x)
+  printf("Hello, %s-san!\n", x)
+  printf("%sさんこんにちは!\n", x)
+end
+
+hello2("太郎")
+hello2("Kate")
+hello2("Mike")
diff --git a/kakezan.rb b/kakezan.rb
new file mode 100755
index 0000000..d9ee3e8
--- /dev/null
+++ b/kakezan.rb
@@ -0,0 +1,12 @@
+#!/usr/bin/env ruby
+# -*-coding: utf-8 -*-
+
+def kakezan(x, y)
+  a=x*y
+  return a
+end
+
+puts "2つ数値を入れてください。掛け算した値を返します。"
+x = gets.to_i
+y = gets.to_i
+printf("%d\n", kakezan(x, y))
diff --git a/shikakkei.rb b/shikakkei.rb
index affd4b5..8ad1bfa 100755
--- a/shikakkei.rb
+++ b/shikakkei.rb
@@ -2,9 +2,9 @@
 # -*- coding: utf-8 -*-
 
 def shikakkei(tate, yoko)
-  if tate < 0 || yoko < 0
+  if tate <= 0 || yoko <= 0
     return nil
-    end
+  end
   return tate*yoko
 end