forgot first::SplitNumber.Multiply..

first/Program.cs

@@ -9,6 +9,12 @@
 
             Console.WriteLine(a.First);
             Console.WriteLine(a.Second);
+
+            a.Multiply(2);
+
+            Console.WriteLine(a.First);
+            Console.WriteLine(a.Second);
+            Console.WriteLine(a.Value);
         }
     }
 }

first/SplitNumber.cs

@@ -29,5 +29,12 @@ namespace first
                 Second = value - First;
             }
         }
+
+        public double Multiply(double mul)
+        {
+            Value = Value * mul;
+
+            return Value;
+        }
     }
 }