Dancing with a Traffic Light

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.

Dancing with a Traffic Light

October 5, 2014

When we’re in a hurry, we hate having to stop and wait for a red light, or for that sign with the little red man. People in a rush sometimes just ignore that guy and try to run across before cars drive through, which is dangerous. So some people in Lisbon, Portugal wondered if pedestrians (people on foot) would stop if the little red man moved around and made waiting fun. They hooked up the traffic light to a camera in a big black tent, and when a person danced in front of the camera, the computer made the traffic-light guy move the same way. They made a dancing traffic light! Within minutes people were stopping to watch, and some started dancing themselves. Best of all, 81% more people stopped for the red light than usual, so the game improved safety. Check out the video here!

Wee ones: If you have 2 legs and the dancing traffic light guy has 2 legs, how many dancing legs do you have together?

Little kids: The traffic-light guy’s head has 2 dots in the top row, 4 in the next row, 4 in the next and 2 in the bottom row. How many dots in total? Bonus: The dot-guy’s feet span 8 dots in total, but with a 2-dot gap between them. If his 2 feet are the same, how long is each foot?

Big kids: If 27 people each danced for the camera for 2 minutes each, how many minutes of dancing traffic light did passersby get to watch? Bonus: If normally 300 people walk through that intersection and only 160 stop for the red, but with the dancing light now half of the lawbreakers stop with them, how many of the 300 walkers stop now?

The sky’s the limit: If the traffic light has 32 dots across and 32 up and down, and in one dance move the little guy spans 12 dots across and 20 up and down (with his head at the top), how many different places on the screen can he land and fit his whole body?





Wee ones: 4 legs in total.

Little kids: 12 dots. Bonus: 3 dots each, since together they have 6 of the 8 dots.

Big kids: 54 minutes. Bonus: 230, since half of the 140 lawbreakers (70) stop with the 160.

The sky’s the limit: First, figure out how many places the little man can be in a given row. If he’s all the way to the left, his right shoulder is on the 12th dot. If he moves over 1 dot, he reaches the 13th dot as his 2nd possible position. So the number of places is the total width minus 11 (the 11 places he can’t be since he’s too wide), giving him 21 positions across. Going up and down in each of those columns, if he’s at the very top his feet reach the 20th dot, and if he moves down a notch he’s at the 21st dot…so his total places are 32 minus 19 (which are the first 19 places he’s too tall for), giving us 13 spots. The total places is the number of rows times the number of columns, which is 13 x 21 or 273 places he can be.

And thank you Laurel P. for sending this fabulous video!

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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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