It’s the Friday Puzzle!


First, for those of you going to the Cheltenham Literary Festival, I am doing a joint event about the paranormal with writer A L Kennedy on Saturday.  Details here.

OK, here is the puzzle.

John and Erica live together and between the two of them have three chores to perform.  The chores are (i) vacuuming the floors, (ii) mowing the lawn and (iii) feeding the baby.  Each of the chores takes thirty minutes, and they only have 1 vacuum cleaner, 1 mower and 1 bottle of milk.  What is the shortest amount of time in which John and Erica can complete the chores?

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 the Kindle (UK here and USA here) and on the iBookstore (UK here in the USA here). You can try 101 of the puzzles for free here.



59 comments on “It’s the Friday Puzzle!

  1. Niki Lin says:

    Heheh the moment I started to think this was way too easy it hit me 🙂

  2. lehcyfer says:

    one minute – had to scribe a diagram 🙂

    • katie k says:

      I made a diagram too! I got an answer in about two minutes, but I’m only 99% certain it’s correct.

  3. Raymond says:

    Got it 🙂

    If it was a ride on Mower could I mow while feeding the baby?

  4. dcmonk79 says:

    I really don’t like chores!

  5. T9sus4 says:

    If it was a single mother, the answer would be simple: “5 minutes, while she’s baking the cake, doing the dishes and organising the child minder”.

  6. M says:

    Got two answers, depending on the skills of the baby.

  7. Jack Walton says:

    They don’t need to cut the grass as they have a couple of cows in the garden who chew it right down to a lovely length!

  8. AMWhy says:

    A minute thinking it was too easy, then a second realisation that my answer was too slow. 1mim and 1 second total for the answer.

  9. who to say they won’t call in a nanny, a house keeper and a gardener while the wife watches Oprah reruns and the husband play Xbox games. but i do think i have the answer 😀

  10. says:

    It critically depends three factors:

    1 what percentage of each chore can each perform unattended by the other?

    2. are the chores interruptable and resumeable?

    3. do the vacuum and mower have separate power leads?

    • M says:

      Can you stop vacuuming and resume later?

      You can answer that question right?

    • gemma says:

      > You can answer that question right?

      It seems to me that is the core question. If each chore has to be done in one go, the total time needed would be different.

      So if, say, one of the three tasks was skydiving rather than lawn mowing, we’d get a different answer

  11. Emlyn says:

    It seems too easy, am I missing something?

  12. Geoff Geoffty-Geoff says:

    As is often the case with these puzzles this is either incredibly obvious, or I’ve misunderstood it. Knowing me, probably the latter.

  13. Gib says:

    10 seconds for a couple of answers, depending on whether or not you have a one-handed vacuum and a sling that can hold a feeding baby….

  14. Alex says:

    A project manager’s dream question 😉

  15. Kirsty says:

    There’s a baby involved and they’re trying to do the chores in the shortest time possible. Therefore it will take all day.

  16. Anonymous says:

    I live in a country manor get the sevants to it. What!!!

  17. Richard says:

    Drew a diagram and then it was obvious.

  18. Berhard says:

    i think it is easy,
    The second solution would require a record player of the manufacturer “dual”… or a baby carryage,…

  19. Chris says:

    They must have a big house if it takes half an hour to vacuum it!

  20. Bletherskite says:

    Well i got an obvious answer in about 10 secs so as usual I’m doubting my answer as it seemed to easy.

  21. Norfolk in Goog says:

    Surely it depends on if the milk is bottle or tit

  22. Berber Anna says:

    I’ve got an answer that’s probably the one that’s intended (as indicated by the ‘bottle of milk’ statement), but if she breastfed and used a sling, it’d be faster (as I see someone has also stated above).

  23. Rob says:

    Divide and conquer!

  24. fredb says:

    got it before i finished reading the question – so does that count as negative time?

    This is similar to “how long to cook three burgers when only two can be grilled at a time, and each side of each burger needs to cook for 1 minute”.

  25. Alan says:

    With Richard’s puzzles, if the answer is obvious, there is usually a catch. With this one, I don’t think there is 😦

  26. SeleneBlueSky7 says:

    Now, this is outrageously impossible! 😀 Horrible puzzle!

  27. drupp says:

    I have two answers. One depends on who the baby is.

  28. Kristian says:

    I have 3 different answers.
    One with no premises added.
    One with obvious premises added.
    One with super crazy premises added.

  29. RyderDA says:

    Three hours. John’s a guy and refuses to help with feeding or vacuuming. Erica gets mad and storms around the house yelling at John. John goes down to the pub for a pint. Erica is left to do everything by herself. The baby’s nap is interrupted by the vacuuming, and then the kid won’t take the bottle. John gets back to the house to find Erica carrying the baby while trying to vacuum. John figures it’s better to stay outside so decides to mow the lawn. By the time he’s finished, the vacuuming has calmed the baby, Erica is talking to him again, and the baby will finally take the bottle. Happened to me just last week (though my name’s not John).

  30. barry p says:

    do they own a roomba?

  31. Hazel says:

    Why isn’t she breastfeeding? Unless maybe she expressed…?

  32. fluffy says:

    I don’t suppose either of them can multitask…

  33. SherryH says:

    I think I’ve got it. Did not time myself, but under a minute to arrive at my answer. (I like Kirsty’s suggestion, though. Definitely rings true!)

  34. Hmm, well… I got an obvious answer in about 20 seconds, but I’m now thinking its a little TOO obvious based on so many clever comments. Hmm.

  35. Ed says:

    The Surgeon was his mother.

  36. Daniel Brady says:

    I got it in like 5 seconds but realised it couldn’t work, then annoyingly I got the same answer but in a different way. 40 sec

  37. Julia says:

    2 answers, one of which is realistic but vague.

  38. soonerdvm says:

    I got it instantly… as soon as I read it. Which makes me suspect I’m missing something.

  39. Frank says:

    Well I think I have solved it but really need to know the answer from you before I pat my back ! ! !
    Check the brainteasers here –

  40. ldymac says:

    Really tired of math word problems like my school textbks. that made me hate math forever. P.S. Did very well with farmer brown and which car or train wins and math in general. Just bored me ever since. Even my math wizard husband has tired of these puzzles.

  41. ChasTiv says:

    About 20 sec. Answers from RyderDA and Kirsty were pretty good. And seeing these chores are repeating, the answer could be “never”.

  42. Manue says:

    Can the baby hold the bottle by himself? We do not know how old he is. The baby could be breastfed even if they have a bottle at home. Do they have a babycarrier to feed the baby while vaccum cleaning? And are they high tech people with good salaries? Does the vaccum cleaner cleans on its own? Same question for the mower.

  43. Jerry says:

    I “solved it” right away. It seems too easy to be correct. I am assuming either the baby can hold the bottle itself or one of the parents wears a Baby Bjorn.

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  45. Clement Gong says:

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