Back in the 1700’s, a scientist named Carl Linnaeus decided that while mushrooms, germs and starfish are all living things, they don't really belong in the same category or "kingdom." After all, they don’t look anything like each other, do they? So he came up with a system for grouping all living things, with crazy names like "echinoderms" for the group that includes starfish.
Since germs and mushrooms aren't quite as cute, let's stick with starfish for a moment. Since Linnaeus' time, 1,800 “species” or types of starfish have been identified. The different types can have anywhere from 5 to 50 legs, and if a starfish loses a leg, it can just grow a new one through regeneration. When you start with 50 legs, it's hard to imagine you'd notice you're missing one, but apparently they keep count.
Wee ones (counting on fingers): If you have 2 regular 5-legged starfish, how many legs do they have in total?
Little kids: If you have 2 regular 5-legged starfish and 1 more unusual 12-legged starfish, how many legs do they have all together? Bonus: If you have a bunch of starfish with either 5 legs or 12 legs, how many of each type do you have to have if they sport 34 legs all together?
Big kids: If you get 52 starfish as pets, and 16 at most can live together in one bathtub, how many bathtubs do you need to hold them all? Bonus: If you stick them all on your 4 bedroom walls as decoration, with the same number on each wall, how many starfish do you stick on each wall?
Wee ones: 10 legs.
Little kids: 22 legs. Bonus: 2 of each kind.
Big kids: 4 bathtubs, since 3 bathtubs will hold only 48. Bonus:13 starfish per wall.