From Whale Fat to Wax

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.

From Whale Fat to Wax

December 23, 2015

Candles light up all kinds of special times: birthdays, religious holidays, and your house when the power goes out and it’s dark. Of course, way back before we had electricity, everyone needed candles for light. It all started in ancient China and Japan, with candles made of whale fat (yuck). Thankfully, people switched to beeswax hundreds of years later. Before we had clocks, people also started using candles to tell time: candles that melted down a certain amount each hour could tell you how much time had passed. A candle flame burns by melting the wax on top and pulling that fuel up the “wick,” the string in the center. The fatter the candle, the more wax to burn, so the longer it takes to melt each layer. So why do we stick little skinny candles on birthday cakes? Some say that started with the Greeks, who made round cakes to honor Artemis, their goddess of the moon: they’d light candles all around the cake to make it look like the full moon. When you get old enough, your birthday cake will shine bright like that, too!

Wee ones: If you’re turning 4 years old and need 1 extra candle for good luck, how many candles does your birthday cake need?

Little kids: If your cake has 4 candles, your friend’s has 8, and your cousin’s has the number halfway between, how many candles does your cousin have?  Bonus: If you have 3 cake candles that each last 10 minutes, how long can they light the room if used 1 at a time?

Big kids: If 2 candle flames light up the room as much as 1 light bulb, how many candles can match a roomful of 8 lamps?  Bonus: When you make a round candle twice as wide, you’re stacking 4 times as much wax in each inch of height — so it will take 4 times as long to burn. If a candle takes 13 minutes to burn an inch, how long will it take a candle twice as wide?




Wee ones: 5 candles.

Little kids: 6 candles.  Bonus: 30 minutes.

Big kids: 16 candles.  Bonus: 52 minutes, which is almost 1 hour.

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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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