Since April is Math Awareness Month, it’s also Financial Literacy Month — after all, we use numbers every day with money. Money lets us buy food, clothes, and other things we need, but it can also buy some really weird stuff. On the website eBay, people sell their unwanted stuff to each other, like eyelashes for your car (you stick them over the front headlights) or sunglasses for your dog (“Doggles”), as we see here. The catch is, everyone who wants to buy something “bids” on it: they secretly say how much they are willing to pay, and whoever says the biggest number wins and gets to buy it. It all depends how badly your dog wants shades!
Wee ones: If you bid $5 for those Doggles and your friend bids $4, which of you bid more? Who will get to buy them?
Little kids: If you buy a green striped singing stuffed elephant for $6, and someone buys it from you for $8, how much more money do you have now than before you bought it? Bonus: If someone else suddenly bid $5 more than the $8 bid, how much money will that person pay you?
Big kids: You can buy Doggles in 12 different colors. If they have 1 yellow pair in stock but 2 pairs of each of the other colors, how many pairs do they have? Bonus: The car eyelashes sold for $13.99. If you had bid double that, how much would you have paid for them? (Hint if needed: If they had been exactly $14, how different would your answer be?)
The sky’s the limit: If you buy 5 pairs of Doggles each in a different color — say red, yellow, blue, green and black — and you and your dog each choose a pair to wear, how many different color combos could the two of you be wearing?
Wee ones: You bid more, since 5 is more than 4, so you’ll get to buy them!
Little kids: $2 more. Bonus: $13.
Big kids: 23 pairs, since they’d have 24 if they had 2 of each. Bonus: $27.98.
The sky’s the limit: 20 different combinations. For each of the 5 colors you wear, there are 4 remaining colors from which your dog can choose. If you wear red, your dog can wear yellow, or blue, or green, or black, making 4 combos. If you instead wear yellow, then your dog could wear red, blue, green, or black, adding another 4…and so on. By the time you try all 5 colors, you’ve created 5 sets of 4 combos, making 20 total.
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.