I don't remember who, but someone taught me how to do this when I was a kid. Mobius Strip Trick: a fun and simple activity, to wow kids and adults alike; something to do when people say, "I'm bored!"
What you will need: Paper, tape and scissors.
How to: Make some strips of paper.
Cut a page of magazine into six strips. To make the strips longer, taped two together.
Now there there are three strips. Each strip will become a hoop.
Make your hoops:
Hoop 1, on the left - take the strip and tape the ends together.
Hoop 2, in the middle - put one twist in the strip before taping together.
Hooop 3, on the right - put two twists in the strip before taping together.
Are you ready? Here comes the trick part.
Cut Hoop 1 down the middle, and go all the way around.
What do you get? Two hoops.
Cut Hoop 2 down the middle, and go all the way around.
What do you get? One giant hoop.
Cut Hoop 3 down the middle, and go all the way around.
What do you get? Two interlocking hoops!
Hoop 3 is my favourite.