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

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

  1. 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”.

  2. 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!

  3. 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.

  4. 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?

    1. > 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

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

  6. 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….

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

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

  9. 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).

  10. 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”.

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

  12. 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).

  13. 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!)

  14. 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

  15. 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.

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

  17. 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.

  18. 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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