Re: [計量] 請問兩題數學..
※ 引述《retawaet (retawaet)》之銘言：
: 1. Seven one-dollar bills are to be distributed among Lucia,
: 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 receives at least $3
: Column B
: The total number of ways to distribute the Bills
: 分配問題...我忘了T.T~
: 從幾個取幾個有多少取法這類的我會 可是分配的忘記了..
A: 只少有一個人拿到三塊錢以上
= 全部分法 - 沒有任何人拿到三塊錢以上
7塊錢 三個人分 有可能沒有任何人拿到三塊錢以上嗎?
所以選C
: 2.At a sale, the cost of each tie was reduced by 20 percent
: and the cost of each belt was reduced by 30 percent.
: Column A
: The percent reduction on the total cost of 1 tie and 2 belts.
: Column B
: 25%
: 我寫A...可是答案是D
: 為什麼無法比較呢?
: 麻煩幫解惑 感激不盡
設領帶$a 打折後0.8a
..皮帶$b ......0.7b
A: (0.8a+0.7b)/(a+b) = ??????
選D
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