diff --git a/site/content/tutorial/08-stores/04-derived-stores/app-a/stores.js b/site/content/tutorial/08-stores/04-derived-stores/app-a/stores.js
index f5e7eb28a5..407d5ba3a9 100644
--- a/site/content/tutorial/08-stores/04-derived-stores/app-a/stores.js
+++ b/site/content/tutorial/08-stores/04-derived-stores/app-a/stores.js
@@ -14,5 +14,5 @@ const start = new Date();
 
 export const elapsed = derived(
 	time,
-	$time => {}
-);
\ No newline at end of file
+	$time => Math.round(($time - start) / 1000)
+);