GRE Prep Club Daily Prep
Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.
Customized
for You
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
A popular website requires users to create a password consis
[#permalink]
05 Oct 2017, 20:36
05 Oct 2017, 20:36
4
11
Bookmarks
00:00
Question Stats:
55% (01:34) correct
44% (01:37) wrong based on 112 sessions
Hide Show timer Statistics
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
[#permalink]
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
[#permalink]
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!
