Quick, which orange circle is bigger? Believe it or not, both orange circles are the same size! The blue circles are playing a trick, or optical illusion, on you. An optical illusion is a picture that looks different from what is really happening. The different sizes of the blue circles surrounding the orange circles make this trick work. Try covering up some of the blue circles with your fingers or a piece of paper to see the truth!
Wee ones: Point to one of the bigger blue circles, then count up all of them! How many bigger blue circles are there?
Little kids: If there are 8 small blue circles and 6 big blue circles, how many more small blue circles are there? Bonus: How many blue circles does that make all together?
Big kids: How many circles would you have to add to the picture to have 20 total circles? Bonus: If you show this illusion to 24 people and 1/3 of them figure out the truth, how many people get fooled by it?
Wee ones: There are 6 bigger blue circles on the left side of the picture.
Little kids: 2 more small blue circles. Bonus: 14 blue circles.
Big kids: 4 more circles, because there are 16 circles already in the picture. Bonus: 16 people get fooled. 1/3 of 24 makes 8 people that don’t get fooled, and 24 – 8 = 16.
Laura Bilodeau Overdeck is founder and president of Bedtime Math Foundation. Her goal is to make math as playful for kids as it was for her when she was a child. Her mom had Laura baking before she could walk, and her dad had her using power tools at a very unsafe age, measuring lengths, widths and angles in the process. Armed with this early love of numbers, Laura went on to get a BA in astrophysics from Princeton University, and an MBA from the Wharton School of Business; she continues to star-gaze today. Laura’s other interests include her three lively children, chocolate, extreme vehicles, and Lego Mindstorms.