What I would do:
Move those five slides to the end of the presentation. Create a Custom Show
(Slide Show--> Custom Show) that contains just those five slides. Add a link
from one of the objects on the page before the quiz to the custom show,
being sure to check Show and Return. Now, when you play the presentation,
click the link when you are ready to run the quiz. When you are done with
the quiz, clicking one past it will take you back to the original slide. One
more click and you are on the next slide and can continue. Since the quiz
slides are now at the end of the presentation, they won't interfere with the
numbering of the main presentation.