Register    Login    Search    Rss Feeds

Forums Home » Ask An Instructor » GMAT Math » General Math Questions


 Page 1 of 1 [ 5 posts ] 



  Print view Print view Previous topic Previous topic | Next topic Next topic
 

Possiblity

Author Message
patrickgong6688
 Post subject: Possiblity
 Post Posted: Fri Jul 08, 2011 12:08 pm 
Offline
Forum Guests


Posts: 10
A four character password consisits of one letter of the alphabet and three different digits between 0 and 9, nclusive. The letter must appear as the second or third character of the password .How many different passwords are possible.?
A5040 B18720 C26000 D37440 E52000
The answer is D
Can someone give me a reply ?
Top 
varun_783
 Post subject: Re: Possiblity
 Post Posted: Fri Jul 08, 2011 2:31 pm 
Offline
Course Students


Posts: 263
Hi Patrick,

Please specify the source of your question. They must be from a valid source. Please check the forum rules to make sure that it is not from a banned source.

Also, please tell us what you do not understand about the question

Thanks

Sunil
Top 
patrickgong6688
 Post subject: Re: Possiblity
 Post Posted: Fri Jul 08, 2011 8:17 pm 
Offline
Forum Guests


Posts: 10
Hi there ,

This question came from a book which was bought in china.This book was writen by a famous chinese teacher who tought GMAT Quantitative in a prestigious school which is Neworiental for many years.His name is Chenxiangdong.
For this question , I counted as below but it did not work . 10X35X8X7+10X9X34X7=41020. Did I miss something?

Best regards,
Patrick
Top 
varun_783
 Post subject: Re: Possiblity
 Post Posted: Sat Jul 09, 2011 1:31 am 
Offline
Course Students


Posts: 263
Hi,

You have to consider two scenarios:

1) The letter appears as the 2nd character of the password:

10 x 26 x 9 x 8 = 18720

2) The letter appears as the 3rd character of the password:

10 x 9 x 26 x 8 = 18720

Adding the above, you get 37440.

I can see that your logic is OK except that you have taken 35 and 34 as the 2nd and 3rd character. I am assuming that you have done this because you counted the letters and the numbers for that position. This is not right. The questions clearly states that the password must have a letter. By taking 35 and 34, you are including the passwords that contain no letters at all.

Hope this makes sense

Regards

Sunil
Top 
jnelson0612
 Post subject: Re: Possiblity
 Post Posted: Thu Jul 14, 2011 11:57 am 
Offline
ManhattanGMAT Staff


Posts: 1857
As always, thanks Sunil!

_________________
Jamie Nelson
ManhattanGMAT Instructor
Top 
Display posts from previous:  Sort by  
 
 Page 1 of 1 [ 5 posts ] 





Who is online

Users browsing this forum: No registered users and 0 guests

 
 

 
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to: