You can download the template here and cut it out or make it on card. Try the puzzle yourself.
Either make a square with 5 pieces or make a square with 6 pieces.
Click here for the Make Squares worksheet. If you don’t have a printer you can easily make your own jigsaw pieces. You can choose any right angled triangle whatsoever and then make your jigsaw using that triangle;the worksheet gives instructions for this.
The third challenge is to explain this.