diff --git a/collects/teachpack/nuworld.png b/collects/teachpack/nuworld.png
index 4e6d56a352..d17c6500e2 100644
Binary files a/collects/teachpack/nuworld.png and b/collects/teachpack/nuworld.png differ
diff --git a/collects/teachpack/nuworld.ss b/collects/teachpack/nuworld.ss
index a691d968b1..8e70040c11 100644
--- a/collects/teachpack/nuworld.ss
+++ b/collects/teachpack/nuworld.ss
@@ -85,7 +85,7 @@
 
 (define (center base state x)
   (define w (pict-height state))
-  (define d (quotient (- width w) 2))
+  (define d (floor (/ (- width w) 2)))
   (pin-over base x d state))
 
 (define width (pict-height bg))