Heavy Rain That’s Always Dry

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.

Heavy Rain That’s Always Dry

October 2, 2014

When you fly somewhere, you might have to stand around at the airport waiting for your plane. So it’s always good if they’ve set up something cool for you to watch. And an airport in Singapore has done just that, with its Kinetic Rain sculpture. Rows and rows of shiny metal raindrops fly up and down, each on its own string connected to its own motor. As you can see in this video, sometimes the 1,216 drops make nice neat wavy lines, but sometimes they scatter crazily at all different heights. Then sometimes they all make a run for it and hide in the ceiling. It’s the world’s largest “kinetic” or moving sculpture, more than 32 feet long and 13 feet wide. Every one of the raindrops, which are aluminum coated with copper, weighs nearly half a pound. It’s great that they can’t get you wet, but this is rain you wouldn’t want landing on your head, either…better just to watch and enjoy before you head up into the clouds yourself.

Wee ones: If 9 drops in a short row are going up and 7 are going down, are more drops rising or falling?

Little kids: If 16 drops going across ripple down in a wave for 5 seconds and take the same time to ripple back up, how long does the whole trip down and up take?  Bonus: If all but one of the 16 drops across are going up, how many are going up?

Big kids: The drops repeat a 15-minute dance over and over. If during your layover you see 4 full rounds of this, how long have you been waiting?  Bonus: There are 16 equal-length long rows of drops. How many of the 1,216 drops are in each row? (Hint if needed: dividing by 16 is the same as cutting in half 4 times.)

The sky’s the limit: If every 3rd drop starting with the 3rd is falling, every 4th drop starting with the 4th is rising, and the rest are hanging motionless in midair, how many of the first 100 drops are moving?




Wee ones: More are going up (rising).

Little kids: 10 seconds.  Bonus: 15 drops.

Big kids: 60 minutes, which is an hour.  Bonus: 76 in each row. Cutting 1,216 in half 4 times in a row gives you 608, 304, 152, then 76.

The sky’s the limit: 50 drops. There are 33 multiples of 3 from 1 to 99. Then there are 25 multiples of 4 from 1 to 100, but every 3rd one was already counted as a multiple of 3. There are 8 of these multiples of 12 (25 divided by 3 rounded down, or you can count them up: 12, 24, 36, 48, 60, 72, 84 and 96). So there are 33+25-8, or 50 drops on the move.

And thank you Catherine M. for showing us this amazing piece of art!

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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 while still in diapers, 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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