If you’re a regular Mental Floss reader, you know that we love a good brain teaser. And the one below, which originated on Facebook and has been shared more than 150,000 times, is a great one to test just how sharp you are on a Friday evening at the end of a long workweek.

It’s a seemingly simple enough task: spot the error. Your time starts now…

We’ll give you a minute …

And a little space for you to scroll down to find the answer …

 

 

 

 

 

 

 

 

Did you figure it out?

The “mistake” is that the word “mistake” is misspelled on the instruction sheet on the left. If you missed that completely, you’re not alone: the grid of numbers is what immediately grabs your attention.