In a library, books are arranged on a single shelf by publication year. Book X is 12th from the left end. Book Y is 15th from the right end. If there are 4 books between Book X and Book Y, and Book X was published earlier than Book Y (placing X to the left of Y), how many total books are on the shelf?
31 books.
Book X is at position 12 from the left. Moving 4 books past X places Book Y at position 17 from the left (12 + 4 + 1 = 17). Since Book Y is 15th from the right, the total number of books is 17 + 15 - 1 = 31.
About this riddle
Logic riddles give you a few facts and ask what must be true. List what you know, cross out what cannot be, and see what is left.
Difficulty: Medium. More like this: Logic riddles with answers or try Einstein's Logic Grid for a different kind of puzzle.
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