- Math can be abstract, sure, but of course we all know how useful it is to have someone around who can calculate a 22% tip in their head. Lots of calculations are nearly impossible to do in your head, yet we still need to do them. It would be great to be able to do a calulator’s work. The good news is it’s possible to cultivate that skill. For instance, think about being able to recall which day of the week April 15th fell on – in 1980. Pretty impossible, right? Leap year changes the number of days from 365 to 366 every 4th year. Each month has differing number of days. It would be so much easier if all months had, say, 10 days. And easier yet if a year had 100 days. Then we could simply count backwards in groups of 10 and 100 to find the answer.
- Since the years and months are complicated the way they are, we resort to checking our calendars and forgetting how many days there are in some months. It seems to be an impossible task to figure out which weekday April 15th fell on many years ago, and yet ..
- … everyday we calculate numbers from a system based on 12 big groups, repeated twice in a cycle, not 10 groups repeated 10 times … and based on 60 small groups, not 100. We can recall, plan and base important decisions on that system without a “second” thought. And even if that big group of 12 turns into a big group of 24, it usually takes us longer, but we can make a calculation quickly. Of course this system is our clock and its 12-hour, 60 second-per-hour system. The big group of 24 is the military time system and is also easy to work with (some would say easier).
- So yes, it would be difficult to learn how to calculate which day of the week a certain date fell on decades ago, but it can be done. And some humans have the ability to perform those complicated calculations with lightning quickness.
Arthur Benjamin is a mathemagician and with Michael Shermer wrote Secrets of Mental Math. For more suggestions on cultivating this important skill, check out the pdf or the book. And, as you can see from the calendar above, April 15th fell on a Tuesday in 1980.