The Rule of 96 at Country Park

A couple of nights ago, we were talking about laps times and speeds on the 1.6 mile loop at Country Park and I remarked that you could find average speed in miles per hour just by dividing 96 by the time in minutes. But I guess this might not be so obvious if you haven't spent a lot of time thinking about it.

Examples: 10 minutes = 9.6 mph, 9 minutes = 10.67 mph, 8 minutes = 12 mph, 7 minutes = a bit under 14 mph (13.71 actually), 6 minutes = 16 mph, 5 minutes = 19.2 mph.

And it works the other way too: 10 mph = 9.6 minutes or 9:36, 12 mph = 8:00, 15 mph = 6.4 minutes or 6:24, 18 mph = 5.33 minutes or 5:20, 20 mph = 4.8 minutes or 4:48.

Not much of a trick to it. Multiply the length of the route, 1.6 miles, by 60 to get 96. This effectively converts the time in minutes into a time in hours, so the division gives miles per hour. Metric system users can do the same thing, multiplying length in km by 60 and dividing by time in minutes to get kph. Using 2.5 km for the length of the Country Park loop (a bit short, but just as an example...) would give the Rule of 150, and a 5:00 lap works out to be 30 kph, 7:30 to 20 kph, 10:00 to 15 kph, etc.

Isn't math fun?