Krush of K’Nex

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.

Krush of K’Nex

January 17, 2019

We are loving this video of the world-record K’Nex ball roller coaster, and you probably will, too. K’Nex are those cool, colorful snap-together sticks. As with Lego or Tinkertoys, you can add on more and more pieces to make giant shapes and structures. This one, built by Austin Granger, uses more than 126,000 pieces! Balls travel up little elevators, roll down wavy ramps, and ride ferris wheels, all of which together fill a huge warehouse. Blinking lights line some of the paths to add pizzazz. There’s even one of those toilet-bowl drains where the balls circle around and around before going down the hole. See if you can follow all those balls, and guess how many sticks each one actually touches!

Wee ones: The ball “elevators” run up and down a straight line. See if you can spot any straight up-and-down lines in your room.

Little kids: If you snap on a blue K-Nex, then a red, then a white, then a blue to start the pattern again, what color is the 6th stick?  Bonus: How many sticks do you snap together to make a cube? If needed, look at a rectangular box-shaped object to see the edges!

Big kids: If the ball takes 14 seconds to roll to the left on a ramp, then just 1/2 that time to roll back to the right, how long does that whole back-and-forth take?  Bonus: If a new ball starts at that first spiral every 10 seconds, how many balls will start the trip during a 5-minute stretch — including the very first at 0 seconds?

The sky’s the limit: If the 126,000-piece ramp uses equal numbers of red, blue, green, white, and black sticks, but 4 times as many yellow sticks as red, how many sticks of each color does it use?

 

 

 

 

 

 

 

 

 

 

Answers:
Wee ones: Answers might include the vertical (up and down) edges of windows, doors, dressers and other furniture, and stripes in curtains.

Little kids: A white stick.  Bonus: 12 sticks: 4 on the bottom, 4 up-and-down side, and 4 around the top.

Big kids: 21 seconds, since it takes 14 seconds there and 7 back.  Bonus: 31 balls. There are 6 per minute starting at 10 seconds in, then you add 1 more to count the very first.

The sky’s the limit: 56,000 yellow sticks, and 14,000 of each of the other 5 colors. If you have equal numbers of those 5 colors and then 4 times as many yellow as any of them, then each red stick has a blue stick, a green, a white, a black and 4 yellow sticks with it, making a “set” of 9. There are 14,000 of those sets in 126,000, so there are 14,000 of each of the small colors and 4 times as many as that for yellow.

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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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