A ten volume set of books are placed upright, in order, on a shelf (see photograph). Each book is 4.5 cm thick, and has two covers, each of which are .5 cm thick. A bookworm starts on page 1 of volume 1 and munches his way in a straight horizontal line through to the last page of the tenth volume. What distance does the worm travel?
As ever, please do NOT post your solution, but feel free to say whether you have a solution and how long it took you. Answer on Monday. Have a great weekend!
Richard Wiseman 
Strictly speaking, an indeterminate distance. 🙂
I’ve got an answer — it took about a minute. Thanks for the fun!
Nick gets this week’s gold star.
About 30 seconds and then another 30 seconds after an “a-ha” moment.
What unit of measure do you require the answer to be in……? You could make it really tricky by specifying that the distance travelled must be given in the geological unit of “X the size of Wales”
🙂
About 30 seconds – but it makes some assumptions that are not clarified in the question. Can’t really elaborate more without giving it away here… 🙂
Had to read thrice.
Then got it.
Why is it that everyone except physics students get this one right, especially on an exam paper?
Why do you say that? That’s a provocation!
maybe because physics students tend to read articles rather than books 😉
and?…
Oh, I get it, it’s because physics students take at least the double of the time to solve easy problems, than they use in difficult ones. That would explain why they don’t get it in time in exam papers. Lets thinks on one faster to them,… hmmm…
Our bookworm is kind of insecure. After it reaches a cover and crosses it to the other side, there is a 10% chance that it “thinks” best to not continue, to revert direction, to cross the cover again and continue through the book it crossed already… to easy things, whenever he finds open air, it always reverts its direction. So, what is the average distance it will travel until find the last page of the last volume, for the first time?
I’ll explain a solution at Monday to not spoil Richard’s puzzle, this if can get it until there, since I invented the problem right now. But if I can not get it in two days, then it should be really easy for everyone else 😉
About 30 sec, only to realize I was wrong. And then about a minute …
This was a puzzle in a 4th grade spelling book that I taught from years ago.
About a minute, including drawing a sort of schematic
I admit I’ve seen it before, anyway 30 secs. and a smug grin.
Although a tricky one, this is a very well known and old problem. I think anybody having a moderate interest in puzzles and quizzes must have already come across this problem in the past.
Yep, not as touh as earlier puzzles. Still good, though.
The books are moving at the speed of light. The worm cannot move.
Too bleeding long. I must be stupid
Nice and easy, 30 seconds or so. Reminds me of one of my old maths teachers: “Read the bloomin’ question!”
Again with the slight lack of clarity in the description, which can be read two ways, if I’m not mistaken. You could use a good editor on these puzzles!
You assume his wording was a mistake.
Too easy. A doddle compared with last week anyway!
Got it…then oh oh no reread yep made little worm mistake then OK now got it……about a minute all said and done…..but wait…..does the book worm still have all of it’s own teeth? I might be able to tell you how fast it can eat it’s way through if I can know if it has all it’s own teeth….between now and Monday……hehe slowwww weekend……
Hahahaha is a little worm mistake hard to clean up after?
Yeah, about a minute or two, got the wrong answer first time round
Is it a ladened or unladened book worm?
And is it African or European?
1st soldier with a keen interest in birds: Where’d you get the coconuts?
King Arthur: We found them.
1st soldier with a keen interest in birds: Found them? In Mercia? The coconut’s tropical!
King Arthur: What do you mean?
1st soldier with a keen interest in birds: Well, this is a temperate zone
King Arthur: The swallow may fly south with the sun or the house martin or the plover may seek warmer climes in winter, yet these are not strangers to our land?
1st soldier with a keen interest in birds: Are you suggesting coconuts migrate?
King Arthur: Not at all. They could be carried.
1st soldier with a keen interest in birds: What? A swallow carrying a coconut?
King Arthur: It could grip it by the husk!
1st soldier with a keen interest in birds: It’s not a question of where he grips it! It’s a simple question of weight ratios! A five ounce bird could not carry a one pound coconut.
King Arthur: Well, it doesn’t matter. Will you go and tell your master that Arthur from the Court of Camelot is here?
1st soldier with a keen interest in birds: Listen. In order to maintain air-speed velocity, a swallow needs to beat its wings forty-three times every second, right?
King Arthur: Please!
1st soldier with a keen interest in birds: Am I right?
Took me 30 sec to get a (more or less) obvious answer, but later I realised the answer can be any distance between this obvious answer and a figure that depends on the width of the pages, unless we make an assumption, just like CyberFerret said.
About 2 seconds.
This got me thinking – would the answer be the same for a Muslim bookworm?
Yes, it would. What defines the order is the books and the book-keeper, not the worm. Now, if you are talking about manga books, you have an issue here (since how the books are stored, is clearly presented by the photo).
Religion is not as important as language, ask any worm 🙂
Think I have it! Only confusion for me is over whether the entire book (with covers) is 4.5cm thick or whether just the pages themselves are 4.5cm thick, with the thickness of the covers to be added on top of that. I think it’s probably the latter but I don’t think the question makes it absolutely clear. Very good puzzle though, and I enjoyed the “Eureka” moment!
Are the books placed on the shelf in order from left to right? Does the thickness of the book already include the covers or are the covers added on top of the book thickness?
How long is the bookworm? – and actually there isn’t such a species, so a trick question! 😉
OH just great Simon! Thanks what next you gonna say there isn’t a Santa or Easter Bunny Too?
Sadly there is no Santa or Easter Bunny 😦 The Tooth Fairy does it all 🙂
OMG can the tooth fairy tell me if the book worm has all it’s own teeth?
and if I can’t find any book worms I wonder if inch worms could chew their way through in the same time that a book worm with it’s own teeth? OK gotta find me either three book worms or inch worms {just in case the above IS true} that still have all their own teeth… three set of books and see how fast they can chew through those books and then I can say how fast per cm they can chew….. my head hurts now…..
About fifteen seconds of wondering what the “twist” was, followed by one of TS’s “aha” moments, then a fwe seconds (with a calculator!) to get my answer.
*SIGH*
few
Took me about 30 secs, then an ‘oh wait – aha’ moment so another 30 secs. Then I re-read the questions had a bigger ‘oh right-bugger-okay sorted’ moment. So about 2 mins in total.
This seems so simple and obvious I can’t help feeling I must be missing some twist somewhere
I agree. Seems like a straightforward junior school maths problem to me.
Follow your feelings…
Okay – just re-red the question yet again and looked again at the picture, had another big ‘ oh what!, eh! hang on – okay, um, um, um got it!’ So now I have my 4th and final answer.
Less seconds than centimetres covered by the bookworm.
May we assume the books are not Arabic texts? 🙂
About a minute.
Same answer if they were…
I think the answer would be different if the books were Japanese, though.
Oh, wait! Maybe in Japan they would stack the books from right to left… Then, same answer.
I think I got it, but most times I say that I totally failed. When I hear the actual answer I will probably say “oh.”
I’m with you!
GO US!
yep got it.
I think I have it.
Does anybody have a reference about how old this riddle really is? The oldest version I could find in my library was from 1973, but I would imagine that is has been around ever since there were books (printed books?)…
I heard it in the ’60s, but it might have been from a book printed in the ’30s – and it is probably much older than that.
I think I have the right answer, although there’s some serious ambiguity in the question. It took me about 3.5 to 4 minutes.
Hahahaha how can you ignore serious ambiguity…is that not a red flag? Yet, you set it aside and solve the puzzle without the clarity needed. How do you do that?
The answer depends on what language the books are written in.
Does it?
If it’s written in a right to left language, wouldn’t the books be stacked right to left as well?
I do believe the language only matters if the book worm is reading it out loud while chewing…… but I am sure that any well behaved book worm’s mother {mum} would have taught it better.
So there! (LilaByrd landed on your shoulder…brought a smile to your conversation…then flew on to spread more happiness!)
Finally a classic I can actually remember. There have been so many Friday puzzles where I knew I once knew the trick but couldn’t remember it – this makes a nice change!
The question was a bit ambivalent, so I have two answers. (typical psychologist fence-sitting) about half a minute thinking, and half a minute checking the calculations.
Ambivalence is a state of having simultaneous, conflicting feelings toward a person or thing.
Call me persnickety, but can a question have conflicting feelings?
Inquiring minds want to know…
Seconds – quite a nice puzzle, though.
With these puzzles I always wonder how people know they are ‘right’ – as what if you think you have solved it (like I had) and then realise when talking to someone else you hadn’t at all!! sometimes I think you – Richard- should give the answer and ask how it is correct- much harder!
my brother got it in about 15 seconds…..not as hard as usual I think
From page 1 of vol 1 to the last page of vol 10, eh?
Would be more solvable if it it were the first page of vol 1.
Page “1” can appear quite a way into a book, after the frontispiece, preface, ToC, plate list and introduction on pages i, ii, iii etc.
Honestly I don’t think the question is ambiguous. I think the two measurements need to be read separately. No-one in their right mind, if asked to pass me a book, would tear the cover off before giving it to me. The cover is part of the book. No ambiguity.
The answer depends on whether volume 1 is on the left of the picture (behind volume 2) or on the right (in front of volume 2). This is not clear, as the picture is tiny and the numbers on the volumes indistinct.
It also depends on wether the 4.5cm thickness includes the covers or if the pages are 4.5cm thick.
With these two unclear variables, I get 4 possible solutions.
2 seconds – wrong answer
2 minutes – probably the right answer
I think the distance from Vol 1 first page to Vol 10 last page is shorter than Vol 1 last page to Vol 10 first page…
Tried this as a practical experiment once.
My wife got up early one morning and took volume 4 out just as the worm was in transition between volume 3 and 4.
The early bird got the late worm…
hehehe….
This is an old one. Very easy when you have heard it before.
Well, I got a very, very simple algebraic answer, but clearly I’m missing the real point of the question. I’ve read it several times and I’m still not getting it. It’s gonna be a long weekend if I can’t figure this one out. Is it against the rules to leave a hint in the comments?
Line up ten books, don’t worry about thickness, and “be” the worm.
Thanks, I think I got it.
“Ten-volume book set” is in the singular… 😉
Like many others here, my first solution took about a minute. After a thorough rereading, I believe my second solution is correct.
Read then reread the question, so think I got the correct anwser first time after about 1 minute. Wakes my brain up though!
I came to the “right” answer very quickly. Then realized the “real right” answer after considering the comment about the page widths which gave me my “a ha” moment. Although there are some giveaways in posts after that, they only became giveaways after my own “a ha” moment. If I “read” them right. [pun alert]
the page widths are included in the original dimensions. the answer is really clear, as long as the books are arranged in numerical order.
Well, I see there are infinite ways to cross the books as stated in the problem (straight & horizontal), it’s minimum distance being the (not so) obvious answer and the maximum being a value which depends on the width of the pages.
I don’t think this width is stated in the problem. Just in case you thought otherwise, I am not referring to the pages thickness, but to the distance from the spine to the outer edge of the pages.
Exactly, jh. It’s curious that Richard went to the trouble of eliminating the ambiguity due to one dimension (the vertical), but neglected to address the transverse dimension. I guess it’s all part of his social psychology experiment.
Many versions of this problem sidestep this issue by giving the number of pages in each volume and asking how many pages the bookwork munches through.
Took some double checking, since at first it looked like a simple math problem. I think I spotted the trick. Call it two minutes.
Urgh it took me ages!
The answer is 11001.
Oh no! I posted the ASCII codes and the site translated them, please delete Wiseman.
Haha, did you think I would give the answer THAT easy? You’re right, but you’re still wrong.
Pheew! Felt like a complete schmuck, should have known better.
TOOK ABOUT 2 MINUTES TODAY; THIS IS AN OLDY BUT GOODY!
About 10 seconds because of “seen it before”.
I’m surprised everyone hasn’t seen this one before. It’s a good puzzle, I think. No algebraic formulas necessary, just some very simple math.
Simon is right. You may be a genius, Richard, but your use of the English language should be more meticulous.
His use of the language is not the problem…he writes very carefully…our ability to think out of the box is. He is testing our reaction to the concept of ambiguous language. Hello? Heh LLLOOOOOO? hehehehehe
Go back and look at the past Friday Puzzles. Do you really think he is such and idiot that he mistakenly changes puzzles that are very old and very well known in exactly the same way every week?
go back…go baaaack….
What is the _width_ of each book? 😉
About 30 seconds. Figuring out the answer was easy. Figuring out the problem took most of the time.
It took me like 5 minutes and I only figured it out because I knew I had the wrong answer and looked up the right one on a different site. I’m also pretty sure I’ve seen this puzzle before, but I still couldn’t quite make the jump without cheating.
4 minutes, but could Richard have found a more out of focus image? Agree with others about the ambiguities, but assumed the covers and rest of the book thickness are separate measurements i.e. book with covers = 5.5cm.
A couple seconds which makes me wonder if I’m missing something but it seemed straightforward.
45 seconds and then a couple of minutes wondering what I might have done wrong before I figured I’d go ahead and post anyway;
Dead easy.
Be careful the things you deem to be “dead” easy…it may be a prophetic choice of words, friend.
Ach! Images of book worms make me cringe. Can we maybe stay away from literary massacres in the future? I don’t think my stomach can take it…
Oh, and the puzzle is appallingly simple grade school arithmetic.
Hahahaha appalling!
The question must say in which language the books are written in order to solve it. Assuming its any language that uses roman writing, it took me about 15 secs
Good point. Never thought of that.
Well, I think that the photograph spoke to that fact. I can’t see what the books are, but they’re certainly in Roman script, which implies that the books read from left to right.
It took me about a minute, I think.
I hope it’s that simple. =D
about 10 seconds to solve, and then a minute of, “could it really be that simple?” before I confirmed my answer.
Physics, schmizics…
It seems so obvious, but then again some things do…
I’m dubious about my answer…but I CAN wait
My first time here, and loving it like crazy. The puzzle made me smile, made me think 1 minute was sure I had the answer. Then I read all the comments and had to go back and check again, and now well I am puzzled over this puzzle and look forward to reading the answer on monday
Don’t wait for Monday, friend…go back and look at all the other Friday Puzzles…and don’t forget to read all the comments…then, you may understand.
OOOOHHHHHH! OKay, I was going nuts so I googled it (sorry) and now I understand!
Good puzzle. Like many above, I spent about half a minute on the wrong answer before seeing the trick. Another half minute to get the right answer (I think) and double-check it.
Not difficult, but not obvious either – at least to someone with my mindset. (Perhaps I should have studied physics.)
And I agree – the wording is ambiguous as to whether the 4.5cm includes the covers or not. Not a big deal, but with the crowd these things attract it’s probably worth paying attention to such details.
“A ten volume set” IS not “are.” Is that the right answer?
About a minute to get to the point where I *think* I’ve solved it.
I expect, though, to take sixty hours or so waffling over whether I actually got it (i.e., until you post the answer on Monday. ;))
well…the 10 seconds or so it took me to do the math…though I am off by the thickness of a couple pages of book…but I figure I’m close enough
Hahahahaha “Close enough” is a brilliant theme for this blog! Ahahahaha kills me…
Had it before I finished the question. I made up this question to fool a friend when I was ten years old. i was *sooo* disappointed when I found out years later that I wasn’t the first!
Dont post such stupidly easy ones. Do you know that in India every school going child will answer this right without blinking.
jay: Well, 90% of them will undoubtedly give the wrong answer unblinkingly, but this is certainly an elementary school level problem.
And how thick is the bookworm?
Ahahaha how thick are the people who can’t follow the rules? (Or ignore ambiguous language?) Hugs!
“on”, not “at”. As asked, you actually do need the width of the bookwork to derive the correct answer.
I have it. It took about three seconds after I finished reading the paragraph… One check, and … yeah…
… does it matter if he is in the woods and the tree that fell and was used to make the paper for the books made a noise and startled the bookworm? …
oh young one you must take a journey down the yellow brick road and seek the great oz for your own “aha!” moment and then and only then shall you find your answer!
(Spoken in voice of Yoda) “Knows much, Lilabyrd does…wise, she is.”
It took me less than a minute to say 54cms.
Lo importante no es la solución, ni el tiempo. sino el juego de deconstrucción y reconstrucción puesto en juego. La incertidumbre es aquí la clave. Un desafío al determinismo racional! Muy buen desafío!
since had already done this in 7th grade algebra concepts 1 it took me about 3 sec. and another 2 for the math.
It’s either ridiculously easy and obvious or I’m missing something. It should have been made clear whether the width included the covers.
think twice and read thrice
i had the same thoughts at last fridays puzzle and felt ambarresed when the solution was posted. :o)
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http://shopadidas.wordpress.com
About 20 seconds, because I realised I had to read the question carefully.
at first it took me 10sec, which was obv too fast. so i started reading again and came to a slightly different solution within 30sec.
i hope its right this time.
About a minute or two. Try it with the books on your own bookshelf.
Of course I’m assuming the books are written in a European language and not in Hebrew or Arabic!
I got it!
A similar one:
How many fence posts do you need for a 10 m fence with one post every meter?
Btw, does the 4.5cm thickness of a book include the two 0.5cm covers, or not?
ahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahah ha haha ha hahaha ha ha haha cough cough hahahahahaha um shrug good question…
I didn’t get the ‘a-ha!’ moment so I think I’m wrong 🙂
I think I got it right away. I’ll see when the answer is posted.
Got this one rather quick, by my own surprise. I am awful at math but figured out the trick within 5 seconds. I nearly broke my arm patting myself on the back!
# Mel Says:
February 20, 2010 at 10:47 pm | Reply
Btw, does the 4.5cm thickness of a book include the two 0.5cm covers, or not?
I kinda agree with Mel’s intent, that the wording is ambiguous, but the best way to read the wording is that the COMPLETE book is 4.5 cm. If I calculated wrong, I and the rest of us only did so because of the ambiguity. If wrong, it just takes a simple recalculation.
I just checked with an English major who agrees with me that “the best way to read the wording is that the COMPLETE book is 4.5 cm.”
For anyone looking for an ah-hah moment, just go to a multi-volume set and open the first volume to p. 1.
May I suggest that you and your friend (the English major) incorrectly assume that it is permitted to decide what is “the best way to read the wording…”?
OK, then, I will.
I suggest that this and every previous Friday Puzzle he has posted has critical information *purposely* omitted. Why? I can guess, but the answer is “I don’t know.”
But, I do know that there is a distinct pattern.
Since I don’t believe he is an idiot who just gets lucky enough to screw it up in a similar way every week, I must assume it is on purpose. But, either way, it is not simply a poorly written puzzle. No, friend…there is clearly mischief afoot…
About 30 second, tough its the first time I have seen this problem.
I’ve got the solution! Just a matter of lateral thinking…!
I think I’ve got it. It took about 30 seconds after reading it twice 😉
10 seconds, just use common sense
Two minutes. So slow.
It took me few seconds
we did this in maths last week. just had to try and remember.
Does the worm have length or is it a point object? 😛 Anyways, I imagined a ‘dimensionless’ worm and I think I got the answer. Waiting for Monday! 😉
Almost immediately – being able to visualise the path helps to get the right answer..
for me it took about 20 seconds after i figured out how to find out the answer
What order are the volumes in?
believe i have it. 30 seconds . first post many other tries. thank you for the fun
G
Less than a minute. How do we know if we’re right?
My first submission, obviously.
The answer is revealed Monday.
Then you join the discussions as to how you were mislead by the way the question was worded.
You got your rage all prepared, TS? I’m thinking about doing my MS Paint tonight.
Problem: the worm would have to curve into the book to start at p. 1 of vol. 1 and curve out — probably opposite the spine — of the last munched page, given that the books are in order from L to R, and page order is a Western standard (I have vols. w/ p. order in reverse).
between 3 and 4 miles,depending on which hemisphere and time of day.
http://www.ihatenikki.com/?mylink=f807796a3c403c24
http://www.ihatenikki.com/?mylink=f807796a3c403c24
Ahahahaha can I get an “I told you so” please? (Tapping on the mic) Is this thing on? (Crickets…)
Lol. i love these puzzles.
OK, everyone, open your minds…open…opennnnn….
Before you can solve a problem, you must have enough information to solve it. “But, how does one determine if there is enough information, teacher?” Well, Grasshopper, if you can reasonably come to more than one answer, then there is not enough information. “But, what is the definition of reasonable, teacher?”
“Young one, many people will never know the answer to that question. They have trouble with the difference between possible and probable…but remember, don’t be afraid to conclude that a question is unanswerable…blindly taking stabs at the answer when clearly ambiguous language exists is as useful as riding a lead balloon in a pickle factory.”
“I still don’t understand, teacher.”
“I know, child, I know. Don’t worry, not everyone is supposed to get it…now go outside and feed the cows.”
A little addition, a little multiplication, real easy. Maybe 20 seconds.
A little too easy, actually. Did I get the right answer, I wonder? Let’sl wait and see…
Eek, no, I didn’t have the right answer. Need to rethink things…
Okay, got what I think is the REAL answer in another 20 seconds.
(Sorry for the triple-post)
The answer would be different if these were Japanese or Arabic books. I will say no more.
I think Levi is catching on…go LEVI!
ive got an answer. took about 20 seconds.
Got the answer in about 10 seconds, then re-read the question and noticed I needed a slight adjustment.
Read carefully.
You don’t tell us whether the covers are counted as part of the book’s width.
I guess it just means that the answer is one or the other, so as long as you know both, you win.
haha great puzzle! got all my workmates thinking in our coffee break today 😀
3.5 i think cause cover is equal to .5.
.5×2=1 4.5-1=3.5
The worm starts at page so it does not go trou the first cover
I drop a comment every time I like a article on a site or if I have something to valuable to contribute on the conversation. It’s a result on the fire communicated in the post I browsed. And after reading this article I had been basically moved enough to drop a comment here
what’s the answer?