Lots of animals can make great pets: dogs, cats, guinea pigs, even flamingos if you have a pond. So what are the most popular household pets? There are two ways to answer this. If you count how many houses have one kind of pet or another, there are more dog houses than anything else — dogs win! But if you count animal by animal, a house can have more than one of an animal. In that case, cats and fish win. There are 81 million cats and almost 76 million fish, but 72 million dogs. Hey, as long as you’re putting fish food in the tank, you might as well have 20 fish in there, right? Rabbits, turtles, and guinea pigs all make the list, too, along with “livestock” like chickens and sheep. Wonder if anyone has one of each!
Wee ones: Who has the most legs, a flamingo, a fish or a dog?
Little kids: If you have 2 cats, 4 hamsters and a ferret, how many whiskery noses do they have? Bonus: If there are 20 houses on your street and all but 1 have a pet, how many homes have pets?
Big kids: 9 million homes have 76 million fish all together. If 8 million homes have just 1 fish, how many millions of fish are left for the rest? Bonus: 43 million houses have dogs, but just 37 million have cats. If 10 million houses in that whole set have both, how many have just 1 kind of pet?
The sky’s the limit: Say all the neighbors on your street have pet hamsters, turtles, and penguins. If the hamsters and turtles add up to 16, the turtles and penguins add up to 10, and the hamsters and penguins add up to 8, how many of each do you have?
Wee ones: The dog, which has 4 legs.
Little kids: 7 noses. Bonus: 19 houses.
Big kids: 68 million fish. Bonus: 60 million homes (33 m dog homes and 27 m cat homes).
The sky’s the limit: 7 hamsters, 9 turtles, and 1 penguin. If you drop from 10 total to 8 total when you change from turtles-and-penguins to hamsters-and-penguins, there must be 2 more turtles than hamsters. They add up to 16, which means if the turtles dropped by 2, they’d be equal and add to 14. So there are 7 hamsters, which gives us 9 turtles. There are 10 pets when you add penguins to turtles, so there’s just 1 penguin.
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.