It’s a lot easier to have legs in pairs. That way you won’t fall over when you walk. We humans have 2 legs, and so do all birds. Mammals like bears and bunnies have 4 legs. All bugs have 6 legs. Spiders and octopus have 8. The one odd man out is the starfish. Most of these prickly, scratchy ocean friends have 5 legs. But there are over 1,800 types of starfish, or “species,” and they don’t have to have just 5 legs — they can have up to 50! Even with all those legs, if a starfish loses one, it can just grow a new leg through regeneration. When you start with 40 or 50 legs, do you even care if you’re missing one? But it looks like these guys keep count.
Wee ones: Hold up 5 fingers to pretend your hand is a starfish!
Little kids: If you have a 5-legged starfish, a 12-legged starfish, and an 8-legged starfish, which one has the most legs? Bonus: Which 2 starfish have 13 legs together?
Big kids: If you have a pile of pet starfish with either 5 or 8 legs, how many of each type must you have if they have 26 legs all together? Bonus: If you stick 50 pet starfish on your 4 bedroom walls to decorate, can you put the same number of stars on every wall? If not, how many leftover starfish do you have? (Assume each star touches only 1 wall.)
Wee ones: See if you can hold up 5 fingers!
Little kids: The 12-legged starfish. Bonus: The 5-legged star and the 8-legged star.
Big kids: Two of the 5-legged ones (10 legs between them) and two of the 8-legged ones (16 legs between them). Bonus: Not quite – you’ll have 12 on each wall, with 2 starfish left over.
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.