GWD11-Q14

[凱薩琳]

A comapny has assigned a distinct 3-digit code munber to each of its 330 employees. Each code number was formed from the digits 2,3,,4,5,6,7,8,9 and no digit appears more than noce in any one code number. How many unassigned code numbers are there?

A.6
B.58
C.174
D.182
E.399

Ans:A

請問這題怎摸算阿？？

[sencerio]

三碼都不能重覆，且三碼只有2.3.4.5.6.7.8.9這8個數字能用(不能用1)

所以 百位數字有8個選擇、十位數字有7個選擇(因為百位數用了一個)、個位數字只剩六個選擇

因此所有有8x7x6=336組可以用， 336-330就是剩下沒用的數字