推 minimumi:原來如此~我會了耶~多謝! 08/26 02:01
※ 引述《minimumi (米尼)》之銘言：
: 41.
: All of the stocks on the over-the-counter market are designated by either
: a 4-letter or a 5-letter code that is created by using the 26 letters of
: the alphabet. Which of the following gives the maximum number of different
: stocks that can be designated with these codes?
: (A) 2(26^5)
: (B) 26(26^4)
: (C) 27(26^4)
: (D) 26(26^5)
: (E) 27(26^5)
: 81.If each term in the sum a1 + a2 + . . . + an is either 7 or 77 and the
: sum equals 350, which of the following could be equal to n ?
: (A) 38
: (B) 39
: (C) 40
: (D) 41
: (E) 42
: 想請問一下這兩題在問什麼?
41.
其實你只要按部就班寫算式即可
方法共有 26^4 + 26^5 = 26^4(1+26) = 27*26^4..............(C)
81.
是說這n項是由7或是77組成的
設共有x個7，y個77
則 7x + 77y = 350，化簡得 x+11y=50
開始湊對有 (39,1)、(28,2)、(17,3)、(6,4)四種情況
得出 n 可能的項數有 40、30、20、10
對照答案選項得到唯一解............(C)
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