Some pets are much happier with friends. Guinea pigs feel safer with other guinea pigs. So in Switzerland, they wrote a law saying you MUST own at least 2 guinea pigs. You may have 2, or 200, or none at all — you just can’t have 1. But when people have 2 guinea pigs and 1 dies from old age, not only are the owners sad, they’re also breaking the law. So a woman named Priska Kung “rents out” guinea pigs. People pay to borrow one of her 80 “meerschweinchen.” People get back half their money if they return the pig, but some love their new friends so much that they just keep them!
Wee ones: If you have 2 guinea pigs and bring in 2 more as friends, how many do you have now?
Little kids: If you must have at least 2 guinea pigs, at least how many little guinea pig legs do they have all together? Bonus: If Priska has 83 guinea pigs and rents out 1, how many does she have now?
Big kids: If you pay $1 per day to rent a guinea pig for 7 weeks, how much does that cost in total? Bonus: If Priska’s 80 guinea pigs each eat 2 cups of dry food and 1 cup of hay every day, how many cups of food do they all eat each day?
The sky’s the limit: If Priska rents out 1/4 of her 80 guinea pigs in November and 3/10 of the ones left in December, in which month did she rent out more?
Wee ones: 4 guinea pigs.
Little kids: 8 little legs. Bonus: 82 guinea pigs.
Big kids: $49. Bonus: 240 cups (3 per pet).
The sky’s the limit: In November. She’ll have 3/4 of the pigs left, and 3/10 of 3/4 is 9/40, which is less than 1/4 (which would equal 10/40). If you want to solve using the number of guinea pigs, she rents out 20 in November, leaving her with 60, and she then rents out 3/10 of the 60 which comes to 18 pigs that month.
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.