Plastic-Gobbling Sea Machine

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.

Plastic-Gobbling Sea Machine

August 5, 2014

It’s exciting when anyone invents a machine that’s going to make our world better, like cleaning up garbage from our oceans. It’s even more exciting when that person is a 19-year-old kid. Boyan Slat has designed an “ocean cleanup array,” a set of white rafts connected by long tubes. The array is floated around a giant garbage patch in the sea, and traps the plastic junk bumping up against the tubes. Eventually the rafts collect the junk, filter out fish and seaweed, and then store the plastic for recycling. Boyan says the arrays could clean up 7,250,000 tons of plastic. There are 5 big areas of ocean where the currents make giant circles that trap the garbage; fish in the worst area, the North Pacific Garbage Patch, eat up to 24,000 tons of plastic every year, and over 1 million seabirds and 100,000 sea mammals (like dolphins and seals) die every year from eating this stuff. It’s clear when you do the math that we need Boyan’s invention.

Wee ones: If of the 5 garbage patches Boyan cleans up the North Pacific garbage circle first, how many areas are left to clean after that?

Little kids: Boyan thinks it will take at least 3 years to build his invention. If he had all the money today and started now, in what year will he finish? (Reminder: Right now we’re in 2014.)  Bonus: If it takes 3 years and 3 months starting now (in August), in what month of that year will it be ready?

Big kids: If each school of fish eats 20 tons of plastic all itself, and you collect 600 tons from an area, how many schools of fish have you saved?  Bonus: How do you say the number “7,250,000”?

The sky’s the limit: It takes thousands of dollars to clean up the tons of garbage washing up on beaches. If a beach has 5 tons of garbage and each ton costs twice as much to clean up as the one before it, how much did the last ton cost if the total costs $62,000?




Wee ones: 4 more areas.

Little kids: In 2017.  Bonus: In November of that year.

Big kids: 30 schools of fish.  Bonus: 7 million two hundred fifty thousand.

The sky’s the limit: The last ton costs $32,000. If the first ton costs c, then the total cost is:
c + 2c+ 4c + 8c + 16c = 62,000
31c = 62,000
c = 2,000 = cost of the 1st ton
The last ton costs 16 times that, or $32,000.

And thank you Catherine M. for sending us this amazing story!

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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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