diff --git a/README.md b/README.md
index 43f597f..d6d15a7 100644
--- a/README.md
+++ b/README.md
@@ -17,3 +17,4 @@
   * [第07章 疑念をテストに翻訳する](https://github.com/at-grandpa/study-tdd/pull/11)
   * [第08章 実装を隠す](https://github.com/at-grandpa/study-tdd/pull/12)
   * [第09章 歩幅の調整](https://github.com/at-grandpa/study-tdd/pull/13)
+  * [第10章 テストに聞いてみる](https://github.com/at-grandpa/study-tdd/pull/14)
diff --git a/part01/spec/money_spec.cr b/part01/spec/money_spec.cr
index c662996..cbcebff 100644
--- a/part01/spec/money_spec.cr
+++ b/part01/spec/money_spec.cr
@@ -30,4 +30,9 @@ describe MoneyPackage do
       MoneyPackage::Money.franc(1).currency.should eq "CHF"
     end
   end
+  describe "testDifferentClassEquality()" do
+    it "クラスが違っても通貨で等価比較できること" do
+      (MoneyPackage::Money.new(10, "CHF") == MoneyPackage::Franc.new(10, "CHF")).should be_true
+    end
+  end
 end
diff --git a/part01/src/money_package/dollar.cr b/part01/src/money_package/dollar.cr
index 8b039ca..e1e7020 100644
--- a/part01/src/money_package/dollar.cr
+++ b/part01/src/money_package/dollar.cr
@@ -3,9 +3,5 @@ module MoneyPackage
     def initialize(@amount : Int32, @currency : String)
       super(@amount, @currency)
     end
-
-    def times(multiplier : Int32)
-      Money.dollar(@amount * multiplier)
-    end
   end
 end
diff --git a/part01/src/money_package/franc.cr b/part01/src/money_package/franc.cr
index cabe75e..f9dc748 100644
--- a/part01/src/money_package/franc.cr
+++ b/part01/src/money_package/franc.cr
@@ -3,9 +3,5 @@ module MoneyPackage
     def initialize(@amount : Int32, @currency : String)
       super(@amount, @currency)
     end
-
-    def times(multiplier : Int32)
-      Money.franc(@amount * multiplier)
-    end
   end
 end
diff --git a/part01/src/money_package/money.cr b/part01/src/money_package/money.cr
index 9eebe05..d284d63 100644
--- a/part01/src/money_package/money.cr
+++ b/part01/src/money_package/money.cr
@@ -1,5 +1,5 @@
 module MoneyPackage
-  abstract class Money
+  class Money
     def initialize(@amount : Int32, @currency : String)
     end
 
@@ -8,10 +8,12 @@ module MoneyPackage
     end
 
     def ==(other : MoneyPackage::Money)
-      (@amount == other.@amount) && (other.class == self.class)
+      (@amount == other.@amount) && (other.currency == self.currency)
     end
 
-    abstract def times(multiplier : Int32)
+    def times(multiplier : Int32)
+      MoneyPackage::Money.new(@amount * multiplier, @currency)
+    end
 
     def self.dollar(amount : Int32) : self
       MoneyPackage::Dollar.new(amount, "USD")