I have thoroughly enjoyed MNN blogger Shea Gunther's recent posts on converting kilometers to miles. I'm a runner, so I'm always trying to figure out how far that 10K run really is (in miles) or just how many 10Ks I need to run to train for a marathon (26.2 miles.)  


Shea's first post, Cool math trick: Converting between miles and kilometers, gave me a quick and easy way to do these conversions in my head — something I have never been able to accomplish before. It also reminded me just how much math I have forgotten since my school years. Fibonacci? The golden spiral? I must have been absent that day — or maybe even that whole semester. With two kids in school, I started to wonder just how long I could hold on to my status as at-home tutor — particularly in the math department.  


Coincidentally, I got an email the other day about a new book that helps parents brush up on their math skills. "Math for Grownups: Relearn the Arithmetic You Forgot From School," by Laura Laing takes readers through lots of "real-life" math scenarios such as comparing the fuel efficiency of two different cars, converting a recipe that feeds four into one that feeds eight, or figuring out if a product on sale at the store is really a "deal."  


Granted, "Math For Grownups" doesn't go beyond elementary school mathematics, and it certainly doesn't touch Shea's Fibonacci series. Laing does offer up the standard miles-to-kilometers-to-miles conversion formulas, but she doesn't have any of Shea's cool conversion tricks. But the book does offer a great refresher in arithmetic as well as some tips for doing everyday math in your head.  


By the way, what I loved even more than Shea's post was how fired up everyone got about it — about math! Some folks were downright belligerent in the comments, while others passionately offered up their own conversion tricks, leading to Shea's follow-up post: More ways to convert between miles and kilometers.  


So now, thanks to Shea, even though my runs are slow, my math is not. But hey, I'm also a sailor. Shea, do you have any cool tricks for converting knots to miles?