In one day at a library, 64 people borrowed books. Twice as many people borrowed only a thriller as borrowed only a science fict

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问题 In one day at a library, 64 people borrowed books. Twice as many people borrowed only a thriller as borrowed only a science fiction book. Three people borrowed a biography only and 11 people borrowed both science fiction and a thriller, but not a biography. The same number borrowed a biography and a thriller but no science fiction as borrowed one of each of the three types. Twenty-one people did not borrow a thriller. One more person borrowed a science fiction book and a biography book than borrowed a biography only.
How many people borrowed a thriller only?

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答案28 people borrowed a thriller only.

解析 (设三种书都借的人数为x, 那么既借传记又借惊险小说的人数也为x;设既借传记又借科幻小说的人数为y;设只借科幻小说的人数为z,那么只借惊险小说的人数为2Z。根据题意可知:y=4;y+z+3=21;3Z+2X+y+11+3=64,故求出z=14,2Z=28.)
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