This quick brain-teaser will leave you puzzled

This is something you've probably never had to think about before. As you'll soon see, we've come up with a quick brain-teaser that'll get the gray matter working overtime. Beware though: we're only giving you a few seconds to work out the solution...

So did you solve the problem in time? If not, there's no need to worry. You can wait for one of our next challenges and try again.