Puff Daddy

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.

Puff Daddy

August 24, 2014

We humans love to build sandcastles, but we aren’t the only ones. Scientists have learned that the pufferfish builds sandcastles, too — but being a fish, it builds them on the ocean floor. Deep sea divers first noticed strange underwater patterns over 20 years ago, but no one knew until now what those shapes were. Apparently male (boy) pufferfish build them as nests to attract female (girl) pufferfish, and make them by swimming in straight lines towards the center to make grooves in the sand. What’s incredible is that pufferfish are only about 5 inches long, and yet their castles can be 6 feet wide or more, like the one in this photo. No wonder it takes the poor fish 10 days to build one! When Puffer finally gets a girlfriend who likes his nest, she lays eggs in the center of it and leaves. The dad stays to guard the eggs until they hatch, then starts all over building a new nest. Hopefully these guys like building sandcastles as much as we do.

Wee ones: What basic shape is the pufferfish “castle” in this picture?

Little kids: The eggs take 6 days to hatch. If a pufferfish lays them today (Sunday) as the first day, on what day of the week do they hatch?  Bonus: If the nest took 10 days to build and the eggs took 6 to grow and hatch, how many days did the whole adventure take?

Big kids: If you take just 3 hours to build a sandcastle, how many more hours does the 10-day pufferfish take? (Reminder: A day has 24 hours.)  Bonus: How many times as long does the pufferfish take compared to you?

The sky’s the limit: If a pufferfish’s castle has 10 grooves in the innermost ring, 12 in the next ring around it, 14 in the next and so on, how many rows does it have if there are 90 grooves?




Wee ones: Circle.

Little kids: Friday.  Bonus: 16 days.

Big kids: 237 hours.  Bonus: 80 times as long (79 times longer).

The sky’s the limit: 6 rings. As you see, for 2 rings it has 10 and 12 grooves, which is the same as 11 and 11 (2×11). With 14 in the 3rd ring, it has 10, 12, and 14, which is the same as 12, 12, and 12 (3×12). Following this pattern, the next ring will make a total of 4×13, the one after will yield 5×14, and the next (6th) ring will yield 6×15 grooves, or 90.

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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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