Math on the Brain

On this morning’s run to Priest Point Park, I was thinking of Ms. Z’s Marysville Middle School mathematicians. More specifically, I came up with a real world word problem for them. Maybe a “do not proceed to high school” until passing problem of sorts.

In Olympia, Washington there’s a beautiful little waterfront community called Boston Harbor. Visit it sometime. Rent a kayak, eat an ice cream bar at the marina, meditate on the Puget Sound. BH is 7 miles from downtown Oly. Traveling from BH to town on BH Rd. the first 5 miles are 40mph and the last two are 30mph. However, it just so happens that Thurston County doesn’t patrol North Olympia’s rural roads. Therefore, half the residents, the Rule Followers, do 40 and 30, but for the other half of Deplorables, like myself, the only deterrent is occasional deer on the road (for the record, I do 45 and 35).

On Monday’s run, a van passed me doing approximately 70mph, today a white Volvo wagon doing 65mph (yes, I am a speed estimating savant). Which got me thinking. How much time does a BH driver save on their way to town if they drive 60mph for the 5 miles designated 40mph, and then stuck behind a Rule Follower, 30mph for the last 2 miles?

I’ll wait.

Here’s my peabrain calculation. Sorry in advance to Ms. Z. for my unconventional approach. First, we need to calculate the Law Obiders travel time. As a cyclist that tends to ride around 18-20mph, I know that at 20mph, it takes 3 minutes to travel 1 mile. Therefore, if we double the speed, we can halve the time, so 40mph = 1:30/mile. So multiply 1:30/mile x 5 = 7:30. At 30mph it obviously takes 2 minutes to travel 1 mile, so 4 more minutes, so BH to downtown Oly in 11 minutes, 30 seconds.


Now what about The No Regarders for the Law? 60mph is 1 minute/mile, so 5 minutes. Then our 4 minutes to cover the 2 mile stretch for a grand total of 9 minutes.

Here’s the tricky part, keep your columns straight people! 11:30 – 9:00 equals a grand total savings of 2 minutes and 30 seconds.

Now a message for my BH friends. If you’re so efficient with your time that you never waste two and a half minutes once you get to your destination, go ahead and speed away, just don’t look for any sympathy when your car is totaled by Bambi. Or leave for work 2-3 minutes earlier?

All good math lessons have extensions, so here’s mine for Ms. Z. Based on available government statistics, calculate the increased likelihood of an accident as a result of increasing one’s speed by 20mph. Then take that increased likelihood and calculate the approximate negative effect on the speeding driver’s life expectancy. I’m guessing it’s greater than 2 or 3 minutes.

Class dismissed.