I am giving lots of talks over the next few days.  On Saturday I am at Think On in Cambridge and performing with the Festival of the Spoken Nerd.  On Sunday I am at the South Place Ethical Society in London and then on Tuesday I am speaking at the Anomalistic Research Unit in London.  Hope you can make it!

OK, to the puzzle.  Five people order a square pizza. The first person dives in an eats a quarter of the pizza. The other four people have to divide the remaining three-fourths into four equal and identically shaped slices. The cuts must be straight. How must they cut the remaining pizza in order to produce four identical slices?

As ever, please do NOT post your answers, but do say if you think you have solved the puzzle and how long it took. Solution on Monday.

I have produced an ebook containing 101 of the previous Friday Puzzles! It is called PUZZLED and is available for theKindle (UK here and USA here) and on the iBookstore (UK here in the USAhere). You can try 101 of the puzzles for free here.

1. I may be wrong, but have we not seen this one before, maybe with a different description?

1. We have, but last time it did not say ‘three-fourths’, so I imagine it was copied and pasted from a better source.

I am really disappointed by this flagrant use of US English.

2. David D says:

Oh, first post! It took 10 secs to solve. Really.

1. David D says:

Well nearly first post!

3. M says:

I’ve seen this one before, but not on this site.

I know the answer, but I hope people are not going to complain about not having the same size of crust.

1. Navneeth says:

Did you mean to say, “same shapes of crust”? 😉

4. Ale says:

Well, I saw it just a couple of days ago. But trying to solve it then took me quite a while.

5. Anonymous says:

I solved it in about 2 minutes.

6. Goliath says:

I gave myself 10min to find a solution. Jotted down the frame with a pen, took my pencil and a rubber to start with a few trial and errors but a mere moment later I got it in the first try. Wow… must be my lucky day.

7. Yvonne says:

1 sec
it’s old, very old…

8. mrsyardbroom says:

Never seen it before but solved in approximately one minute.

9. Hugh Janus says:

Norfolk in Clue

10. Niva says:

An easy old puzzle, so I knew the solution right away.

11. Wayne Kerr says:

So you have 3 squares, divide each into quarters.. Job done

1. Nick says:

Not quite… It says cut into 4 pieces, not 12 😉

Not seen this one before but not a difficult puzzle to solve. I hope it’s a “take it to the edge” (or whatever they’re called) pizza, otherwise with my solution, some are going to complain about the distribution of crusts…

12. mp4man says:

10 seconds

13. As someone already said the first time you see this it can be quite a challenge but it’s quite well known.

That said, there are some very good, less well known, and challenging variations on it. Wonder if Mr Wiseman (or someone else) can find any online.

I love pizza, but it’s instant weight gain unfortunately. Thought this would be a hard one (oh Matron) but it only took a minute including a little simple maths.

15. JimC says:

About a minute, but then I have a cold.

16. Alistair Frith says:

Sure I’ve seen it before, maybe on this site. I’m usually not great at these but I think I got this one and it only took a few seconds.

17. Jason says:

Oh yes! Got it! Eventually…
Just have to find the lowest common denominator! Lol!

18. Mickey D says:

10 secs!

19. Paul Durrant says:

A few seconds. Possibly because I’ve seen similar puzzles before.

20. Berhard says:

if the straight cuts may be stopped in the middle of the pizza, then no problem…

under a minute

other solutions i did not find…

21. About 1 second to think I knew the answer, and 30 seconds to draw a diagram to check I was right.

22. Hilary says:

About half a second – would have taken longer without the helpful diagram.

This puzzle doesn’t make sense. Why do they have to be the same shape?

1. Nick says:

Have you never been involved in a pizza-war?!!

or course they have to be the same shape! and the greedy 1st person has to do extra chores to make up for their gluttony 😀

2. Nick, why do they have to be the same shape?

Why would the four complain if they each got the same amount, but not the same shape?

Yours sincerely,

uneducated in the ways of pizza etiquette.

24. Charles White says:

Got it in about two minutes.

25. Anonymous says:

Wow this was actually really easy 🙂

26. I’ve got it! 5 seconds! Am I smart or is that very easy?? 😉
have a nice weekend

27. It took me a little less than a minute, I think. Most work involved looking for a decent pen ^_^

28. Richard says:

I started by doing the maths to work out how big each piece would be. After that it was easy.

29. Anonymous says:

Good one …

X X X X X X
X X
X X
X X
X _ _ X
X ] X
X ] X
X X X X X X ] _ _ X
X ] ] X
X ] ] X
X ] _ _ _ ] X
X I X
X I X
X I X
X X X X X X X X X X X

1. Anon says:

Is that Morse code for “I can’t do this puzzle?”

30. Ohepelia Balls says:

Good one. If you take a stochastic, transformational approach and run this using Hergoves Regression it suddenly becomes clear ..

X X X X X X
X X
X X
X X
X _ _ X
X ] X
X ] X
X X X X X X ] _ _ X
X ] ] X
X ] ] X
X ] _ _ _ ] X
X I X
X I X
X I X
X X X X X X X X X X X

31. Anonymosity says:

I was overthinking it. Once I turned my brain off, it was easy

32. Daemon says:

2/9 + 1/36 for each

33. Duncan says:

Took 4 attempts, quite easy once you realise it’s not as easy as you might think at first – if you see what I mean…

34. CH23 says:

Easy-peasy
About 20 seconds before it hit me.

35. Tom (iow) says:

Got it in 5-10 minutes. Off to play Tetris now.

36. Seen this one before. Nice solution though.

37. One Eyed Jack says:

What a “cheesy” puzzler.

38. Lazy T says:

LLLLa a a a z z z z y y y y T’s seen this before,
y a a a a a wn

39. Michael Fishman says:

I think I have it solved. It took only a few seconds.

40. kirarak says:

So is it possible to end a cut in middle of a pizza or it has to be from straight from edge to edge?

1. Mort Canard says:

Cuts will be ended and started in the middle of the pizza.

41. Mort Canard says:

My first guess turned out right so about 5 seconds.

42. RModule says:

Have not seen this one before.. Maybe 30 seconds.

43. Notsuoh says:

We were given this puzzle to solve back in primary school. Easy!

Test only

45. Mal says:

GOt it after a few minutes of thinking, was quite straight forward once I got there!!

46. way too old says:

An ancient puzzle. 2 very old youtube videos in the past three days.

This isn’t a history blog, Richard 🙂

47. dharmaruci says:

this is trivial. needs just 2 diagnogal cuts.

but what if pizza is round with quarter missing? harder yes?

1. Eddie (@edzeteito) says:

The two diagonal cuts I think you have in mind lead to two different sizes, in which case it would seem the puzzle as it stands is already hard enough for you.

2. dharmaruci says:

attempting hard puzzles is good for the brain so i shall continue eddy despite your advice/

the op (original puzzle) wants identical shapes not sizes. different sises are allowed by the op.

3. Eddie (@edzeteito) says:

But it says “…four *equal* and identically shaped slices…”

That’s the whole point – that they each get the same amount.

I would complain if two others got twice as much as me, which would be the case in your 2-diagonal scenario.

48. Not difficult. Got it after ruling out first attempt. 2nd worked. Maybe 1 minute.