Have you ever watched a movie in 3D? You wear funny glasses that make everything look closer or farther away. Every shape in the movie is drawn in both blue and red, with each blue shape shifted to the left. The red lens lets one eye see only the blue shapes, and the blue lens lets your other eye see only red. The bigger the gap between them, the bigger and closer that object looks. It’s copying how your two eyes see differently from each other because they’re spaced apart (hold your finger near your face, then close one eye to see it “jump”!) Scientists have wondered whether insects see in 3D, too. So they put teeny tiny 3D movie glasses on a praying mantis, and found out that yes, mantises can tell whether objects are close or far away. Of course, now those bugs want to watch movies!
Wee ones: A praying mantis has 2 eyes. Do you have more or fewer eyes than that?
Little kids: If you and your pet mantis go to the movies, how many legs do you have altogether? (As an insect, a mantis has 6 legs). Bonus: If 7 bugs go to the movie and you have 10 pairs of glasses for them, how many extra pairs do you have for people?
Big kids: If there are 18 moviegoers, and there are twice as many bugs as people in the crowd, how many are there of each? Bonus: If there are 29 moviegoers and every 4th one is a bug (while the rest are people), what’s the greatest number of bugs you can have?
Wee ones: Neither — you have the same number!
Little kids: 8 legs. Bonus: 3 pairs.
Big kids: 12 bugs and 6 people. There are 2 bugs for each person, making sets of 3, and there are 6 sets. Bonus: 8 bugs. There would be only 7 if the 4th one was a bug, then the 8th, etc., but if the FIRST moviegoers is a bug, then you have the 5th, 9th and other numbers 1 more than a multiple of 4. So you can fit in an 8th at 29.
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.