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A popular website requires users to create a password consis
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05 Oct 2017, 20:36
05 Oct 2017, 20:36
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Question Stats:
55% (01:31) correct
44% (01:34) wrong based on 105 sessions
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A popular website requires users to create a password consisting of digits only. If no digit may be repeated and each password must be at least 9 digits long, how many passwords are possible?
A. 9! + 10!
B. 2 x 10!
C. 9! x 10!
D. 19!
E. 20!
Kudos for correct solution.
A. 9! + 10!
B. 2 x 10!
C. 9! x 10!
D. 19!
E. 20!
Kudos for correct solution.
Re: A popular website requires users to create a password consis
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05 Oct 2017, 21:50
05 Oct 2017, 21:50
4
Bunuel wrote:
A popular website requires users to create a password consisting of digits only. If no digit may be repeated and each password must be at least 9 digits long, how many passwords are possible?
A. 9! + 10!
B. 2 x 10!
C. 9! x 10!
D. 19!
E. 20!
Kudos for correct solution.
A. 9! + 10!
B. 2 x 10!
C. 9! x 10!
D. 19!
E. 20!
Kudos for correct solution.
Here there are two possibilities - (since it has asked for atleast 9 digit)
1. At least 9 digit
2. all 10 digit
in first case
Choosing 9 digit without repetition = 10 * 9 * 8 * 7 * 6 * 5 * 4 * 3 * 2 = 10! (since any number multiply by 1 is the number itself)
Choosing 10 digit without repetition = 10 * 9 * 8 * 7 * 6 * 5 * 4 * 3 * 2 * 1 = 10!
Therefore total no. ways = 2 * 10!
Re: A popular website requires users to create a password consis
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08 Jan 2020, 21:42
08 Jan 2020, 21:42
1
for 9 digit, possible no= 10.9.8.7.6.5.4.3.2=10!
for 10 digit, possible no =10.9.8.7.6.5.4.3.2.1=10!
Total= 10!+10!=2*10!
for 10 digit, possible no =10.9.8.7.6.5.4.3.2.1=10!
Total= 10!+10!=2*10!
