A bookworm eats from the first page of an encyclopedia to the last page in a straight line. The encyclopedia consists of ten 1000-page volumes and is sitting on a bookshelf in the usual order. Not counting covers, title pages, etc., how many pages does the bookworm eat through?
On a book shelf the first page of the first volume is on the “inside”, so the bookworm eats only through the cover of the first volume, then 8 times 1000 pages of Volumes 2 – 9, then through the cover to the 1st page of Vol 10 for a total of 8,000 pages.
Note: The question asks how many pages, not how many sheets of paper.
Because the first and last volume are not included in the page count. When sitting on a shelf, the front of the first volume is on the right and the back of the last volume is on the left. So there is 2,000 pages that the worm does not eat through.Thus the diagram they tried to provide, just not very well. I ask my students a similar problem, just using measurements for the book volume and covers as opposed to pages. Say each volume is 1″ and the covers are 1/4″ thick, worm starts on page one of book A and eats to last page of book D… similar puzzle. works good for math class and even in the professional world!
@Scott You didn’t like my brilliant diagram?! I am mortally wounded. However, I concur with your comment, because it’s technically correct (the best kind of correct.)
10 Comments on "The Bookworm"
Dinesh Bhimsaria says
October 21, 2016 @ 02:38
8002
Scott says
December 5, 2016 @ 09:40
Why would the answer not be 10,000?? The reasoning makes absolutely no sense.
Bridget says
December 6, 2016 @ 07:25
Difficult logic
Isla says
July 18, 2018 @ 15:19
I agree with Scott!
Chris says
March 2, 2019 @ 16:27
The riddle says to ignore covers. Why are you including them?
Chris says
March 2, 2019 @ 16:30
5010. Ten volumes of 501 sheets
Dan says
March 3, 2019 @ 12:10
@Chris Mentioning the covers is not the same as counting them. And the riddle asks for the number of pages, not sheets of paper.
Scott says
March 7, 2019 @ 09:31
Because the first and last volume are not included in the page count. When sitting on a shelf, the front of the first volume is on the right and the back of the last volume is on the left. So there is 2,000 pages that the worm does not eat through.Thus the diagram they tried to provide, just not very well. I ask my students a similar problem, just using measurements for the book volume and covers as opposed to pages. Say each volume is 1″ and the covers are 1/4″ thick, worm starts on page one of book A and eats to last page of book D… similar puzzle. works good for math class and even in the professional world!
Dan says
March 7, 2019 @ 16:53
@Scott You didn’t like my brilliant diagram?! I am mortally wounded. However, I concur with your comment, because it’s technically correct (the best kind of correct.)
no-one says
June 22, 2021 @ 19:44
it is 5.2
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