Today From Bedtime Math: What You're Really Wearing

Take a closer look at how your clothes come together, in this fun problem from Bedtime Math!
By Laura Overdeck
Apr 21, 2015

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Apr 21, 2015

When you put on a shirt or pants, you can see the colors and patterns: that it's bright green, or blue and white striped, or some other combo. But have you ever looked closely at how your clothes are made? If you look at them through a magnifying glass to see what the threads are actually doing, you might be amazed. The left photo here shows blue jeans, which are woven: some threads run up and down while others run side to side through them. And the right one shows a turquoise T-shirt that's knit, where 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 cotton and wool into skinnier threads and weave them into softer cloth. If you can find a magnifying glass, look at your clothes in a whole new light and find out what you're really wearing.

Now see if you and your kids can come up with the answers to these clothes-inspired math questions.

Wee ones: If your jeans weave together white, blue and black threads, how many colors is that?

Little kids: If your shirt crosses 2 up and down stripes with 2 stripes across, how many places do they 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 blue threads are there?  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 overlaps.  Bonus: 9 overlaps.
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 share the center. Once you bump up to 77 threads, the 39th becomes the middle one, with 38 threads before it and 38 after it.

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