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https://www.wsj.com/articles/folding-paper-can-smooth-out-problems-11675955453

Mathematician Eugenia Cheng explores the uses of math beyond theclassroom. Read more columns here.

I recently had to send a paper letter for the first time in years, so I found myself folding a sheet in thirds to put it in an envelope. When I was growing up I was baffled about how to estimate the thirds accurately. Finally I learned to roll the paper up and then flatten it, rather than making the folds one at a time.

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This copy is for your personal, non-commercial use only. Distribution and use of this material are governed by our Subscriber Agreement and by copyright law. For non-personal use or to order multiple copies, please contact Dow Jones Reprints at 1-800-843-0008 or visit www.djreprints.com.