“See a penny, pick it up, and all day you’ll have good luck!” Today in America we celebrate National Lucky Penny Day: even though 1 penny by itself can’t buy much. Back in the 1800s, though, it used to be worth a lot: a penny could buy a candy bar, sheets of paper, and pieces of cloth to make clothes. Thanks to “inflation” (money becoming weaker over time), a penny isn’t worth very much today. Now you might need 50, 70, or even 100 pennies to buy a candy bar. That’s why people happily put them in penny-crushing machines to stamp pictures on them, like the one shown here — and they pay an extra 25 cents along with it to run the machine! The question is, will that penny still bring you good luck?
Wee ones: What shape is a real, unsquashed penny?
Little kids: If you find a penny each day — Sunday, Monday, and so on — how many do you find in 1 week? Bonus: If you put in the penny plus 25 cents to make a stamped penny, how much money do you spend in total?
Big kids: If you’ve been collecting lucky pennies, and just 1 more will bring you to 1 dollar (100 pennies), how many do you have? Bonus: If you have 85 cents, how many funny squashed pennies can you make if it costs the extra 25 cents to stamp one, and how much money will you have left over?
Wee ones: A circle – and in 3D, it’s actually a very short, squat cylinder.
Little kids: 7 pennies. Bonus: 26 cents.
Big kids: 99 pennies. Bonus: 3 squashed pennies, which will cost 78 cents (25+25+25+1+1+1). You’ll have 7 cents left over.
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.