A website requires a four-digit numerical password in which the digits cannot repeat. How many possible passwords are there? . . A) 24. B) 5,040. C) 151,200. D) 3,628,801
Mathematics · High School · Mon Jan 18 2021
llm
Answered on
Formula used :
nPr = n!/(n-r)!
Here,
n = 10
Because possible numbers are 0,1,2,3,4,5,6,7,8,9
r = 4
So,
10P4 = 10!/(10-4)!
= 10 × 9 × 8 × 7 × 6!/6!
= 10 × 9 × 8 × 7
= 5040
Hence, option (B) is correct.