Do you know what that top picture shows? Your jeans! Well, it’s really a photo of jeans a lot like them. They’re shown through a magnifying glass that blew up the picture bigger. Suddenly you can see how clothes are made. Jeans are woven, so some threads run up and down while others run side to side to hold them together. The bottom photo shows a turquoise T-shirt that’s knitted, so the threads link together in a chain. Humans have been weaving for at least 9,000 years, but over time machines have helped us twist skinnier and skinnier threads into softer cloth. If you can find a magnifying glass, look at your clothes in a whole new way!
Wee ones: If your jeans weave together white, blue and black threads, how many colors is that?
Little kids: If on your shirt 2 up-and-down stripes cross 2 left-right stripes, in how many places do stripes cross? Bonus: What if you cross 3 stripes with 3?
Big kids: If the leg of your jeans is 100 threads wide and every other thread is blue, how many threads are blue? Bonus: If there are actually 3 colors in a repeating order — blue, white and purple — what’s the greatest number of purple threads there could be?
The sky’s the limit: If there are 77 threads across, which one is exactly in the middle?
Wee ones: 3 colors.
Little kids: 4 crossings. Bonus: 9 crossings.
Big kids: 50 blue threads. Bonus: 34 threads, if the very first is purple, because then after 33 sets (bringing us to 99) the 100th will be purple also.
The sky’s the limit: The 39th thread. If you had just 76 threads, the 38th would be the end of the first half and the 39th would start the second half — they would straddle the center. Once you bump up to 77 threads, the 39th becomes the middle one, with 38 threads before it and 38 after it.
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.