Today I am in Norway promoting Paranormality and giving a couple of lectures.  Details here. OK, to the puzzle….

To make French toast, I have to fry both sides of a slice of bread for 30 seconds. However, my frying pan can only hold two slices of bread at once. How quickly can I make three slices of French toast?

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. Phew a nice easy one this week. I had an answer by the time I had read to the end and it took only about a minute to prove to myself that the solution worked.

  2. Damn. I hate puzzles like this – it seems so simple, so I’m wondering what I’m getting wrong. I can even prove that I have the right answer and I’m worried.

  3. Yes, just like a previous one.

    But, suppose the pan is circular and the pieces of bread are exactly square and two whole slices of bread fit into the pan…….

    Maybe there is a quicker solution….

  4. Wow, that was easy…
    Had the idea almost instantly… took me about 30s to verify. But it is a nice happy feeling to be able to solve these puzzles 🙂

  5. Solved almost instantly. It had to mime the actions to confirm. Messy solution though.

    Did not factor in cinnamon or strip though.

    Mmmm, French Toast…

  6. Not really a puzzler is it?

    You buy a clam grill big enough for 3 slices and do them all in 30 seconds. Simple. 😉

    Better yet, you buy a waffle iron and some nice blueberry waffles instead.

  7. Isn’t this just a reworking of a previous puzzle? Anyway, got it! I recognised the problem immediately so it only took about 15s including pen and paper check.

  8. Got it before I finished reading the puzzle. 3 tasks that take a minute to perform, only two can be done at a time.

    Been there, done that.

  9. As long as it’s purely the ‘cooking’ time of the toast we are calculating then the answer was immediate.

    However if ‘making’ the french toast involved buying, rearing or growing the ingredients (as well as combining them) then we don’t have enough data to be able to accurately answer the question.

  10. How many seconds does it take to shuffle one slice out of the frying pan and another one in?

    I would agree that one piece of French toast won’t be up to gourmet standards.

  11. I’ve just spotted a smiley “:)” at the bottom of this web page. Do I get a/the prize??!! I think this is the secret purpose of the Friday puzzle – to see who spots it first.

  12. Well, probably 3-4 minutes. But unlike others here who used one nanosecond I had to convince myself that my upper bound also was a lower bound! The problem is not solved by merely presenting an algorithm which does the kitchen work faster than the naive approach – it also has to be the optimal one.

  13. Oops. I should also add that I watched your appearance at Skavlan and that is why I googled your name and hence found this fine blog of yours. Too bad the other guests weren’t up for rationale.

  14. About 3 seconds for an answer. Then re-cosidered for about 3 minutes. Decided not to bother cutting any of the bread. Back to answer #1. Which i think is wrong.

  15. Well I have an answer, it seems to easy though so I may well have got it wrong. Just looked at my working out again though and think I have got it right as I haven’t fallen into the obvious trap!
    Yay Me!

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