diff --git a/app/Concert.php b/app/Concert.php
index b71ca09..dd39c94 100644
--- a/app/Concert.php
+++ b/app/Concert.php
@@ -34,14 +34,32 @@ class Concert extends Model
         return $this->hasMany(Order::class);
     }
 
+    public function tickets()
+    {
+        return $this->hasMany(Ticket::class);
+    }
+
     public function orderTickets($email, $ticketQuantity)
     {
         $order = $this->orders()->create(['email' => $email]);
+        $tickets = $this->tickets()->take($ticketQuantity)->get();
 
-        foreach (range(1, $ticketQuantity) as $i) {
-            $order->tickets()->create([]);
+        foreach ($tickets as $ticket) {
+            $order->tickets()->save($ticket);
         }
 
         return $order;
     }
+
+    public function addTickets($quantity)
+    {
+        foreach (range(1, $quantity) as $i) {
+            $this->tickets()->create([]);
+        }
+    }
+
+    public function ticketsRemaining()
+    {
+        return $this->tickets()->whereNull('order_id')->count();
+    }
 }
diff --git a/database/migrations/2016_11_08_210440_create_tickets_table.php b/database/migrations/2016_11_08_210440_create_tickets_table.php
index a4cc2ef..383c51f 100644
--- a/database/migrations/2016_11_08_210440_create_tickets_table.php
+++ b/database/migrations/2016_11_08_210440_create_tickets_table.php
@@ -15,7 +15,8 @@ class CreateTicketsTable extends Migration
     {
         Schema::create('tickets', function (Blueprint $table) {
             $table->increments('id');
-            $table->unsignedInteger('order_id');
+            $table->unsignedInteger('concert_id');
+            $table->unsignedInteger('order_id')->nullable();
             $table->timestamps();
         });
     }
diff --git a/tests/unit/ConcertTest.php b/tests/unit/ConcertTest.php
index 9e933d8..9d1769f 100644
--- a/tests/unit/ConcertTest.php
+++ b/tests/unit/ConcertTest.php
@@ -64,4 +64,24 @@ class ConcertTest extends TestCase
         $this->assertEquals('jane@example.com', $order->email);
         $this->assertEquals(3, $order->tickets()->count());
     }
+
+    /** @test */
+    function can_add_tickets()
+    {
+        $concert = factory(Concert::class)->create();
+
+        $concert->addTickets(50);
+
+        $this->assertEquals(50, $concert->ticketsRemaining());
+    }
+
+    /** @test */
+    function tickets_remaining_does_not_include_tickets_associated_with_an_order()
+    {
+        $concert = factory(Concert::class)->create();
+        $concert->addTickets(50);
+        $concert->orderTickets('jane@example.com', 30);
+
+        $this->assertEquals(20, $concert->ticketsRemaining());
+    }
 }