The digits 1,3,4,5,8 are randomly arranged in a row to form a 5-digiit number.
a) How many possible 5-diigit numbers can be formed?
b) Find the probability that the 5-digit nuumber formed is
(i) divisible by 5
(ii) less than 54000
排列與組合難問(5-digit number)?
2016-02-04 4:33 pm
回答 (1)
2016-02-04 5:31 pm
✔ 最佳答案
a)5! = 120
Suppose the 5-digit number can be expressed as 10000A + 1000B + 100C + 10D + E
b)
P(divisible by 5)
= P(A, B, C, D ≠ 5 , E = 5)
= (4!×1) / (5!)
= 1/5
c)
P(less than 54000)
= P(A = 1 or 2 or 3) + P(A = 5, B = 1 or 3)
= (3×4!)/(5!) + (1×2×3!)/(5!)
= 7/10
收錄日期: 2021-04-23 23:44:33
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20160204083320AAXxHJ9