GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 25 Jun 2019, 15:06

Close

GMAT 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

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Close

Request Expert Reply

Confirm Cancel

N! is ending with x zeroes. (N + 3)! is ending with (x + 2) zeroes. Ho

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

 
Director
Director
avatar
P
Joined: 19 Oct 2018
Posts: 554
Location: India
N! is ending with x zeroes. (N + 3)! is ending with (x + 2) zeroes. Ho  [#permalink]

Show Tags

New post 24 May 2019, 18:57
5
00:00
A
B
C
D
E

Difficulty:

  55% (hard)

Question Stats:

62% (02:48) correct 38% (03:11) wrong based on 13 sessions

HideShow timer Statistics


N! is ending with x zeroes. (N + 3)! is ending with (x + 2) zeroes. How many such N's will exist, given N is positive integer less than 50?

A. 5
B. 6
C. 7
D. 8
E. 9
Senior Manager
Senior Manager
avatar
G
Joined: 20 Jul 2017
Posts: 341
Re: N! is ending with x zeroes. (N + 3)! is ending with (x + 2) zeroes. Ho  [#permalink]

Show Tags

New post 24 May 2019, 20:08
nick1816 wrote:
N! is ending with x zeroes. (N + 3)! is ending with (x + 2) zeroes. How many such N's will exist, given N is positive integer less than 50?

A. 5
B. 6
C. 7
D. 8
E. 9


We have to understand that to increase 2 number of 0's, (n+3) should have either '25' or '50' {25x4 = 100, 50x4 = 200) and 'n' SHOULD NOT have any of '25' and '50'. Only then there would be an addition of 2 0's

So, possible values of n are 22, 23, 24, 47, 48 and 49.

IMO B.
ISB School Moderator
User avatar
G
Joined: 08 Dec 2013
Posts: 456
Location: India
Concentration: Nonprofit, Sustainability
GMAT 1: 630 Q47 V30
WE: Operations (Non-Profit and Government)
Reviews Badge CAT Tests
Re: N! is ending with x zeroes. (N + 3)! is ending with (x + 2) zeroes. Ho  [#permalink]

Show Tags

New post 24 May 2019, 20:20
2
nick1816 wrote:
N! is ending with x zeroes. (N + 3)! is ending with (x + 2) zeroes. How many such N's will exist, given N is positive integer less than 50?

A. 5
B. 6
C. 7
D. 8
E. 9


I've used two concepts-

1. In any n! the number of zeroes is primarily contributed by 5s in the product. (we have more 2s in comparison to 5)
2. Box Function- to calculate the number of zeroes in a factorial. Trailing Zeroes: https://gmatclub.com/forum/how-many-tra ... l#p2190991

Interesting facts- Number of 5s gets bumped at 25, 50 etc.

Possible combinations: (N, N+3); N<50
22, 25
23, 26
24, 27

47, 50
48, 51
49, 52

So, 6 Ns are possible. B
_________________
Kindly drop a '+1 Kudos' if you find this post helpful.

GMAT Math Book


-I never wanted what I gave up
I never gave up what I wanted-
GMAT Club Bot
Re: N! is ending with x zeroes. (N + 3)! is ending with (x + 2) zeroes. Ho   [#permalink] 24 May 2019, 20:20
Display posts from previous: Sort by

N! is ending with x zeroes. (N + 3)! is ending with (x + 2) zeroes. Ho

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


cron

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne