[計量] 數題數學

看板GRE (GRE入學考試)作者 (蚊子)時間15年前 (2010/11/13 22:36), 編輯推噓5(5021)
留言26則, 6人參與, 7年前最新討論串1/1
這是http://www.greguide.com裡面Q的第三回練習 但是有好幾題我不太懂。 1. Sunita wants to make a necklace. She has 8 beads. How many different choices does she have? ans: 1200 2. On a chess board one white square is chosen at random. In how many ways can a black square be chosen such that it does not lie in the same row as the square? ans: 2002 3. There are 15 points in a plane, out of which 6 are collinear. How many pentagons can be drawn with these points? ans: 2997 我算是2142 謝謝大家不吝給予指教! -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 114.37.132.249

11/13 23:48, , 1F
第一題我覺得是環狀排列耶 可是這樣是7! 不是1200
11/13 23:48, 1F

11/13 23:49, , 2F
樓上你少了翻轉= ='...我也在卡
11/13 23:49, 2F

11/14 00:00, , 3F
對耶 感謝樓上 那應該就是8!/(8*2)=2520吧!
11/14 00:00, 3F

11/14 00:01, , 4F
我是那樣算阿= =...我不懂答案1200
11/14 00:01, 4F

11/14 00:01, , 5F
他前一題是8人一圓桌 答案是5040 這題就1200= ='
11/14 00:01, 5F

11/14 00:01, , 6F
http://ppt.cc/sTZD 搜尋"珠子"
11/14 00:01, 6F

11/14 00:03, , 7F
第二題沒會錯意是西洋棋盤8*8 黑白各半32/32
11/14 00:03, 7F

11/14 00:04, , 8F
不考慮在不在同條線上 黑白各選一有1024種選擇..
11/14 00:04, 8F

11/14 00:04, , 9F
我也在想她怎麼跑出2002...
11/14 00:04, 9F

11/14 00:06, , 10F
所以第一題答案錯!!(踹
11/14 00:06, 10F

11/14 00:35, , 11F
第二題我算32*24=768 第三題2142
11/14 00:35, 11F

11/14 00:41, , 12F
我算第二題32*28=896 第三題2142 ~"~
11/14 00:41, 12F

11/14 01:15, , 13F
第二題32*28
11/14 01:15, 13F

11/14 01:19, , 14F
第二題我也把line算進去了= =?
11/14 01:19, 14F

11/14 01:47, , 15F
我算的是 2520 896 2142 QQ 答案應該有問題吧?
11/14 01:47, 15F

11/14 18:20, , 16F
2142算法是C(6,2)*C(9,3)+C(6,1)*C(9,4)+C(9,5)嗎?
11/14 18:20, 16F

11/14 18:24, , 17F
我的算法5*C(9,3)+C(6,1)*C(9,4)+C(9,5)持續疑問中?
11/14 18:24, 17F

11/14 18:26, , 18F
因為6個點在同直線不是會有覆蓋過其他點的問題嗎?
11/14 18:26, 18F

11/14 18:28, , 19F
還是我誤解了??
11/14 18:28, 19F

11/14 19:15, , 20F
你說兩點重疊? 取共線上第一和第六點時 其邊上會通過
11/14 19:15, 20F

11/14 19:15, , 21F
2,3,4,5點 你是這個意思嗎..
11/14 19:15, 21F

11/14 21:19, , 22F
對阿 是我誤解題目了還是我想錯了嗎??
11/14 21:19, 22F

11/14 23:04, , 23F
通過2345點並不影響 因為妳取16點 其餘忽略不看
11/14 23:04, 23F

11/14 23:05, , 24F
我想就算看他們也在同一條邊上 應該沒影響(吧..
11/14 23:05, 24F

11/15 07:52, , 25F
感謝 想太多了 題目只取五邊形 沒說只限五個點的
11/15 07:52, 25F

04/13 23:53, 7年前 , 26F
感謝 想太多了 題目只 https://muxiv.com
04/13 23:53, 26F
文章代碼(AID): #1Ctg9kBB (GRE)
文章代碼(AID): #1Ctg9kBB (GRE)