Bobby Seagull: 2020, an interesting year for maths enthusiasts!

January 06, 2020

Happy new year Explore members!

2020 – the start of a new decade! Or is it?! As a maths teacher, it should be no surprise that I like paying attention to detail.

2020 is actually the 10th and last year of the 202nd decade. Using the Gregorian calendar, the first year would be year 1 (no such thing as a year 0 unfortunately). Hence the year 10, would be the end of the first decade and the second decade would be begin at year 11. If we follow this logic, 2020 is the last year of the decade and the new decade begins in 2021.

Relish this mathematical fact, but I’d hope you weren’t a grinch at new year parties by pointing out this out to those celebrating the start of the new decade!

The year 2020 offers a neat bit of visual symmetry with a repeating set of double digits (like 1717, 1818 and 1919 previously). It’s a subtle version of a what might be called a synchronistic number. The number 20 itself plays an important role in our counting system.

For those that have studied French, you’ll be aware that the quatre-vingts (four-twenties) is used to mean 80. Even in English, the word “score” means twenty of anything. The lifespan allotted to us mortals in the Bible (“three score years and ten”) and even iconic US President Abraham Lincoln’s phrase (“four score and seven years ago”) confirm that counting in twenties has been widespread. Further back in time around the 4th century AD, the Mayans using a counting system with base twenty (rather than our ten base system).

I’m particularly excited for the 20s, as our new “decade” brings the Explore Learning Mathematicians’ Award grand final at the Natural History Museum. What a historic setting to celebrate the success of fearless young mathematicians.

Why don’t you brush off your mental cobwebs for the 2020s by trying this Countdown style puzzle. Using only the four operations of arithmetic (addition, subtraction, multiplication, division) and any of these six numbers, can you create the number 2020?

100, 50, 10, 7, 5 1


Good luck and happy 2020s!

Bobby Seagull

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