On Sunday, a numerical event will take place that happens only once every thousand years.
The date will be a palindrome in every single country of the world. In other words, the digits will be the same when written forwards or backwards in whichever date format you choose.
In the UK it will be 02.02.2020.
In the US it will be 02.02.2020
In Asia it will be 2020.02.02
Britain and the USA organise their dates differently – we write day/month/year, but they insist on month/day/year – which causes confusion and mutual irritation on both sides of the Atlantic.
Anyway, this Sunday we can put our differences to the side and cherish the only moment in our lifetimes when the world’s dates will be wonderfully aligned.
Here’s another numerical palindrome:
50, 20, 10, 01, 02, 05
It’s the pence value of the UK coins in circulation under a pound.
What is the highest value of UK coins you can have in your pocket without being able to exchange them exactly for a £10 note?
(This puzzle is filed under. ‘Not difficult but you’d be surprised at how many people get it wrong.’)
I’ll be back with the answer at 5pm UK.
UPDATE: The solution is now up here.
PLEASE NO SPOILERS. Instead, please post your favourite palindromes below the line.
Returning to the palindromic date, the Brazilian mathematician Inder Taneja has created a fiendishly ingenious magic square inspired by 02022020. In a magic square, the numbers in each row, column and diagonal all add up to the same number. Taneja goes one step further. His 02022020 magic square is also a magic square when read upside down and when read in a mirror. (When in a mirror the 2s become 5s.) Wow!
I set a puzzle here every two weeks on a Monday. I’m always on the look-out for great puzzles. If you would like to suggest one, email me.
Thanks to John Trevelyan for today’s puzzle.
My latest puzzle book is So You Think You’ve Got Problems?
