PP-T1-PS-39

[funbob]

39. 5583-!-item-!-187;#058&004668

A certain stock exchange designates each stock with a one-, two-, or three-letter code, where each letter is selected from the 26 letters of the alphabet. If the letters may be repeated and if the same letters used in a different order constitute a different code, how many different stocks is it possible to uniquely designate with these codes?

(A) 2,951
(B) 8,125
(C) 15,600
(D) 16,302
(E) 18,278

Answer: (E)

請問總共幾碼的Code???
倒底是怎麼排出來的組合呢？？？
煩請好心人

[Huang Hsin-Yi]

one letter-26種
two letters-26*26種
three letters-26*26*26種

[purpleme]

有點看不懂耶
可以詳細解說一下嗎
謝謝了

[william0625]

one letter-26種

two letters-26*26種

three letters-26*26*26種

有三種獨立事件
each stock with a one letter code 有26種可能
each stock with a two letter code 有26*26種可能
each stock with a three letter code 有26*26*26種可能

所以26+26*26+26*26*26

[william0625]

可以參考PP-T1-PS-41