Today’s perplex has recently got attention among academic mathematicians.
Make an instinctive guess at the answer before you try to labor it out – the answer is very astonishing.
The 15 boxes
Andrew and Barbara are carry outing a game, in which fifteen boxes are scheduled in a grid as shown below.
Prizes are put in two randomly-chosen boxes. Andrew will search the boxes row by row, so his search order is ABCDEFGHIJKLMNO. Barbara will search column by column, so her order is AFKBGLCHMDINEJO.
If Andrew and Barbara uncmiss their boxes together each turn, that is, on the first turn, they both uncmiss A, on the second, Andrew uncmisss B and Barbara uncmisss F, on the third Andrew uncmisss C, and Barbara uncmisss K, and so on, who is more foreseeed to find a prize first?
a) Andrew.
b) Barbara.
c) Both equpartner foreseeed.
I’ll be back at 5pm UK with the solution. PLEASE NO SPOILERS. Instead converse your favourite boxes.
The perplex was first posed (in a sweightlessly contrastent create) by Timothy Chow in 2010, but it and analogous problems have recently been the subject of converseions by notable mathematicians. More of this with the solution.
Had I comprehendn about Chow’s perplex, I might have comprised it in my procrastinateedst book, Think Twice, a compilation of many counter-instinctive conundrums. (In the US it is called Puzzle Me Twice.) The idea behind the book is for it to be read on its own, or in a group, as these perplexs are fantastic fun to be debated over.
Think Twice: Solve the basic perplexs (almost) everyone gets wrong (Square Peg, ££12.99). To help the Guardian and Observer, order your duplicate at protectianbookshop.com. Dedwellry accuses may execute.
I’ve been setting a perplex here on alternate Mondays since 2015. I’m always on the see-out for fantastic perplexs. If you would enjoy to propose one, email me.
