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.

December 27, 2015

The Rubik’s cube is a simple and famous toy. Each of its 6 flat sides, or “faces,” is divided into 9 squares of a certain color, and the layers can be twisted and turned to shuffle those squares. Then you have to figure out how to spin the cube’s layers in the right order to make every side all one color again. There are 43 *quintillion* different ways that the squares can line up (that’s 10 x 10 x 10…until you have 19 10s). People have learned to solve the cube very quickly, though: Lucas Etter holds the world record at just under 5 seconds. And as our friend Tyler M. just shared, robots can solve it just as fast as we can. In a video by ARM Ecosystem, they built a robot that uses sensors to see the colored squares, then uses motors to hold and twist the cube to solve it. The robot has all the sets of steps programmed into it, so as soon as it sees the mix of colors on each face, it can figure out what to do. Let’s see if that fellow can figure out how make pancakes for breakfast, too.

*Wee ones:* If the cube has blue, green, white, orange, red and yellow faces, how many colors is that?

*Little kids:* If the robot turns the top layer, then the left layer, then the right layer, then starts over with the top layer to repeat, which layer does it turn on the 8th move? *Bonus:* If the robot starts solving the cube at 13 seconds into the video and takes 5 seconds, at what time in the video does it finish?

*Big kids:* If you turn the top layer right, then turn the right layer back, then repeat those 2 moves over and over, you’ll scramble the cube in 32 moves, then start solving it in the same number of moves again! How many moves is that in total? *Bonus:* If you take 8 times as long to solve the cube as this 5-second robot, how long do you take?

*The sky’s the limit:* If only 7 of the 9 squares facing you are the same color, how many different ways could the last 2 squares be colored?

Answers:

*Wee ones:* 6 colors.

*Little kids:* The left, since you would have done the right on 3 and 6. *Bonus:* At 18 seconds.

*Big kids:* 64 moves. *Bonus:* 40 seconds.

*The sky’s the limit:* 25 possibilities. There are 5 colors to choose from, so for each of the 5 choices for the first square, you can put any of the 5 colors in the 2nd spot. So you get 5 sets of 5 choices, or 5 x 5 = 25.

And thanks again Tyler for sharing this amazing video!

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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