
[中學] 一題排列組合

想請教一下4和5選項要怎麼看,我只會一條一條畫但還是算錯
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※ 編輯: wizkhalifa23 (223.137.102.182), 09/12/2017 18:00:05
推
09/12 18:02, , 1F
09/12 18:02, 1F
推
09/12 19:00, , 2F
09/12 19:00, 2F
→
09/13 06:10, , 3F
09/13 06:10, 3F
推
09/14 14:38, , 4F
09/14 14:38, 4F
→
09/14 14:39, , 5F
09/14 14:39, 5F
→
09/14 14:40, , 6F
09/14 14:40, 6F
推
09/14 14:43, , 7F
09/14 14:43, 7F
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