[計量] 一些猴哥計量的問題

看板GRE (GRE入學考試)作者 (追夢者)時間15年前 (2010/10/20 19:07), 編輯推噓2(2010)
留言12則, 4人參與, 7年前最新討論串1/1
第60題 In a bowl that contains 20 marbles, 7 are green, 6 are red, and the remainder are blue. Two marbles are to be drawn at random from the bowl without replacement. column a) the probability that one marble is green and the other is red column b) the probability that one marble is green and the other is blue 答案是B 我約略猜的出來會去選B 可是想知道比較正確的想法、算法 第73題 Seven one-doller bills are to be distributed among Licia, Gomez, and Domingo so that each person receives at least $1. column a) the number of ways to distribute the bills so that at least one person receive at least $3 column b) the total number of ways to distribute the bills 這題答案是一樣(C) 不太清楚怎麼算@@ 還有最後 第78題 At a sale, the cost of each tie was reduced by 20% and the cost of each belt was reduced by 30%. column a) the percent reduction on the total cost of 1 tie and 2 belts column b) 25% 答案是D(無法比較) 為什麼咧......? 以上三題 麻煩大家解答了~~ 謝謝大家! -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 140.112.115.226

10/20 19:14, , 1F
60: A是從(7,6)裡面各拿1, B是從(7,7)裡面各拿1
10/20 19:14, 1F

10/20 19:14, , 2F
所以是B的機會比較多
10/20 19:14, 2F

10/20 19:15, , 3F
73題 因為7個東西分三分本來就是至少有一個會拿到3
10/20 19:15, 3F

10/20 19:15, , 4F
兩個選項等價
10/20 19:15, 4F

10/20 19:18, , 5F
78題 因為選項A是說"on the total cost" 也就是問你
10/20 19:18, 5F

10/20 19:18, , 6F
"最後總價"打了幾折 可是由於tie和belt單價都沒給
10/20 19:18, 6F

10/20 19:18, , 7F
因此無法計算
10/20 19:18, 7F

10/20 19:20, , 8F
當然前兩題也是可以列式或窮舉 但是太花時間
10/20 19:20, 8F

10/20 19:21, , 9F
更正我三樓說的 是"至少會有一個拿到3以上" 漏打
10/20 19:21, 9F

10/20 23:48, , 10F
了解了!!! 謝謝回答:)
10/20 23:48, 10F
※ 編輯: nyyfan0325 來自: 114.42.220.209 (10/23 22:01)

12/02 19:21, , 11F
73題 因為7個東西分 https://daxiv.com
12/02 19:21, 11F

04/13 23:51, 7年前 , 12F
A是從(7,6)裡面各 https://moxox.com
04/13 23:51, 12F
文章代碼(AID): #1ClirQLE (GRE)
文章代碼(AID): #1ClirQLE (GRE)