[問題] 奇數偶數問題 from 高分突破 P240
問題：
Jerome wrote each of the integers 1 through 20, inclusive,
on a separate index card. He placed the cards in a box, then
drew cards one at a time randomly from the box,without returning
the cards he had already drawn to the box.
In order to ensure that the sum of all the cards he drew was even,
how many cards did Jerome have to draw?
(1) 19 (2)12 (3)11 (4)10 (5)3
答案是12
但是12張有可能是五張奇數 七張偶數 加起來還是奇數
這題正解應該是多少?
謝謝^^
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推
12/13 00:17, , 1F
12/13 00:17, 1F
→
12/13 00:18, , 2F
12/13 00:18, 2F
→
12/13 00:19, , 3F
12/13 00:19, 3F
→
12/13 00:19, , 4F
12/13 00:19, 4F
→
12/13 00:20, , 5F
12/13 00:20, 5F
→
12/13 00:20, , 6F
12/13 00:20, 6F
→
12/13 10:26, , 7F
12/13 10:26, 7F
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