When you’re really tired, it’s so nice to flop down on your comfy bed. Well, dogs and cats like our beds, too. Some people don’t want to share their bed with scratchy paws and wet noses, but some pet lovers are just fine with it. One couple with 5 cats and 2 dogs finally built a new bed to hold them all! The megabed stretches almost 11 feet across, and fills up half the bedroom. They made it by shoving together a king-size bed and a full bed, then filling in the gap between them. We’re just amazed all those cats and dogs get along so well.
Wee ones: If you count up the 5 cats, what numbers do you say?
Little kids: If the 2 humans, 5 cats and 2 dogs all sleep in the bed, how many animals is that? (We humans are animals, too!) Bonus: If the humans wash the sheets every 4 days and the last time was Tuesday, on what day do they wash them next?
Big kids: When the 2 humans, 5 cats and 2 dogs are all in the bed, how many legs are kicking around? Bonus: If the bed has just 2 pillows and 2 animals get to use them that night, how many pairs of people vs. dogs vs. cats could there be? (You don’t need to worry about the order, nor which person, cat or dog you’re talking about — just the type).
The sky’s the limit: What if you have 3 pillows? What are all the possible triplets of animal types who could use them? (Again, no need to worry about the order or the names — just the types (species).)
Wee ones: 1, 2, 3, 4, 5.
Little kids: 9 animals. Bonus: On Saturday.
Big kids: 32 legs: 28 pet legs and 4 people legs. Bonus: 6 possible pairs. There are at least 2 of each type of animal, so there are 3 pairs where both are the same (2 people, 2 cats, 2 dogs). Then you can pick one of each, giving you 2 pairs that include a person (P-C, P-D), plus C-D.
The sky’s the limit: There are 8 possible sets of pillow users:
– There’s only 1 case where all 3 users are the same: 3 cats (since there are only 2 people and 2 dogs).
– There are 6 cases where 2 animals are the same and 1 is different: 2 people with a cat, 2 people with a dog, 2 cats with a person, 2 cats with a dog, 2 dogs with a person, 2 dogs with a cat.
– Then you have just 1 case where there’s 1 of each type of animal: person, cat, dog.
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.