Cat out of the Bag

Here's your nightly math! Just 5 quick minutes of number fun for kids and parents at home. Read a cool fun fact, followed by math riddles at different levels so everyone can jump in. Your kids will love you for it.

Cat out of the Bag

March 10, 2019

What does it mean when someone “lets the cat out of the bag”? It means the truth comes out, and usually not anything good. People think we say this because of farmers selling pigs hundreds of years ago. Pigs were worth a lot of money, so sometimes a farmer would swap a cat into his cloth bag instead, and pretend it was a pig. If the buyer didn’t notice, the farmer got to keep his pig, but if the cat popped “out of the bag,” the crooked farmer would get caught. The trick worked well enough, though, because the length and weight of a cat matched a piglet closely enough. Grown housecats weigh around 10-11 pounds, but this one here, named Pickles, tips the scales at an amazing 21 pounds. As long as he didn’t meow, he could have fooled anyone.

Wee ones: Who weighs more, an 8-pound cat or a 10-pound piglet?

Little kids: If you bring both a piglet and a cat to the market, how many legs do they have altogether?  Bonus: If the cat weighs 10 pounds and the piglet weighs 20, what do they weigh in total?

Big kids: If Pickles weighs 21 pounds and eats 1/3 of his weight in dry food each week, how much does he eat each week?  Bonus: If you have a bunch of 21-pound cats and 4-pound kittens, how many of each do you need to fill a bag with exactly 100 pounds?












Wee ones: The 10-pound pig.

Little kids: 8 legs.  Bonus: 30 pounds in total.

Big kids: 7 pounds in a week.  Bonus: 4 cats and 4 kittens. Since you’re adding some multiple of 4 to a multiple of 21, and since 100 itself is a multiple of 4, the multiple of 21 has to be divisible by 4, too. So you’ll need 4 cats (totaling 84 pounds) and 4 kittens (for 16 more pounds).

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About the Author

Laura Overdeck

Laura Overdeck

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.

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