Find all School-related info fast with the new School-Specific MBA Forum
Learn more about the recent changes... close

It is currently 21 May 2013, 16:26
Customize  |  Hide

Search
Register
New posts
Unanswered

If p is a natural number and p! ends with y trailing zeros

  Question banks Downloads My Bookmarks Reviews  
  Oldest Best Reply
Search for:
 
Print view
First unread post
Author Message
TAGS:
Manager
Manager
Joined: 08 Oct 2010
Posts: 216
Location: Uzbekistan
Schools: Johnson, Fuqua, Simon, Mendoza
WE 3: 10
Followers: 7

Kudos [?]: 103 [0], given: 974

GMAT Tests User
If p is a natural number and p! ends with y trailing zeros [#permalink] New post 25 Jan 2011, 06:55
00:00

Question Stats:

51% (02:27) correct 48% (00:57) wrong based on 11 sessions
If p is a natural number and p! ends with y trailing zeros, then the number of zeros that (5p)! ends with will be

a) (p+y) trailing zeros
b) (5p+y) trailing zeros
c) (5p+5y) trailing zeros
d) (p+5y) trailing zeros
e) none of them above


Can someone help me how to solve this question? I think, there must be more than one solution method.
[Reveal] Spoiler: OA
3 KUDOS received
GMAT Club team member
User avatar
Joined: 02 Sep 2009
Posts: 11534
Followers: 1795

Kudos [?]: 9560 [3] , given: 826

GMAT Tests User CAT Tests
Top Member of the Month
Re: trailing zeros question (logical approach needed) [#permalink] New post 25 Jan 2011, 07:10
3
This post received
KUDOS
feruz77 wrote:
If p is a natural number and p! ends with y trailing zeros, then the number of zeros that (5p)! ends with will be

a) (p+y) trailing zeros
b) (5p+y) trailing zeros
c) (5p+5y) trailing zeros
d) (p+5y) trailing zeros
e) none of them above

Can someone help me how to solve this question? I think, there must be more than one solution method.


Given: p! has y trailing zeros: \frac{p}{5}+\frac{p}{5^2}+\frac{p}{5^3}+...=y (check for theory on this topic: everything-about-factorials-on-the-gmat-85592.html) --> now, # of trailing zeros for (5p)! will be \frac{5p}{5}+\frac{5p}{5^2}+\frac{5p}{5^3}+...=p+(\frac{p}{5}+\frac{p}{5^2}+...)=p+y.

Answer: A.
_________________

PLEASE READ AND FOLLOW: 11 Rules for Posting!!!

RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory

COLLECTION OF QUESTIONS:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. NEW!!!

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS ; 9 Devil's Dozen!!!; 10 Number Properties set. NEW!!!


What are GMAT Club Tests?
25 extra-hard Quant Tests

Find out what's new at GMAT Club - latest features and updates

Manager
Manager
Joined: 08 Oct 2010
Posts: 216
Location: Uzbekistan
Schools: Johnson, Fuqua, Simon, Mendoza
WE 3: 10
Followers: 7

Kudos [?]: 103 [0], given: 974

GMAT Tests User
Re: trailing zeros question (logical approach needed) [#permalink] New post 25 Jan 2011, 07:16
It is very logical and simple approach.
Excellent, Bunuel!

It seems to me there is no alternative solution method. If there is one I would appreciate your contributions. Thanks.
2 KUDOS received
Intern
Intern
Joined: 09 Mar 2011
Posts: 2
Followers: 0

Kudos [?]: 2 [2] , given: 28

Re: trailing zeros question (logical approach needed) [#permalink] New post 03 May 2011, 10:44
2
This post received
KUDOS
feruz77 wrote:
It is very logical and simple approach.
Excellent, Bunuel!

It seems to me there is no alternative solution method. If there is one I would appreciate your contributions. Thanks.


I solved it this way:

Since the p! has trailing zeros, Let's assume p=10

10! will have 2 trailing 0s (by the method provided by Bunuel)
p = 10 y = 2
5p! i.e 50! will have 12 trailing 0s = 10 + 2 = p + y
VP
VP
Status: There is always something new !!
Affiliations: PMI,QAI Global,eXampleCG
Joined: 08 May 2009
Posts: 1400
Followers: 8

Kudos [?]: 84 [0], given: 10

GMAT Tests User
Re: trailing zeros question (logical approach needed) [#permalink] New post 03 May 2011, 20:34
for p = 10 trailing 0's =
10/5 = 2

for 5p,
50/5 = 10, 50/25 = 2 hence total is 12
Similarly,
for p = 20 trailing 0's = 20/5 = 4
for 5p, trailing 0's = 50/5 = 10, 50/25 = 2 hence total is 10 + 2 = 12
thus we observe,
number of 0's = p + y
example p = 20, y = 4 giving 24.

Hence A.
_________________

Visit -- http://www.sustainable-sphere.com/
Promote Green Business,Sustainable Living and Green Earth !!

Manager
Manager
Joined: 25 Jun 2012
Posts: 72
Location: India
WE: General Management (Energy and Utilities)
Followers: 1

Kudos [?]: 21 [0], given: 15

Re: If p is a natural number and p! ends with y trailing zeros [#permalink] New post 16 Nov 2012, 18:05
suppose p=6
I am taking 6 because it will have 5 & 2 both to become trailing zeroes.

now 6! has 1 trailing zero.

=6/5 = 1 =y

so 5p = 5*6 = 30

new number is 30!.
Trailing zeroes in (5p)! = 30/5 + 30/25 = 6+1 = 7
now here we get 7=6+1=p+y

which is our answer...opt A
1 KUDOS received
Manager
Manager
Joined: 05 Nov 2012
Posts: 84
Followers: 1

Kudos [?]: 15 [1] , given: 39

Re: trailing zeros question (logical approach needed) [#permalink] New post 04 Apr 2013, 19:14
1
This post received
KUDOS
Bunuel wrote:
feruz77 wrote:
If p is a natural number and p! ends with y trailing zeros, then the number of zeros that (5p)! ends with will be

a) (p+y) trailing zeros
b) (5p+y) trailing zeros
c) (5p+5y) trailing zeros
d) (p+5y) trailing zeros
e) none of them above

Can someone help me how to solve this question? I think, there must be more than one solution method.


Given: p! has y trailing zeros: \frac{p}{5}+\frac{p}{5^2}+\frac{p}{5^3}+...=y (check for theory on this topic: everything-about-factorials-on-the-gmat-85592.html) --> now, # of trailing zeros for (5p)! will be \frac{5p}{5}+\frac{5p}{5^2}+\frac{5p}{5^3}+...=p+(\frac{5p}{5}+\frac{5p}{5^2}+...)=p+y.

Answer: A.
Hello Bunuel.... There is a typo in the equation just before putting down p+y... others may get confused....
GMAT Club team member
User avatar
Joined: 02 Sep 2009
Posts: 11534
Followers: 1795

Kudos [?]: 9560 [0], given: 826

GMAT Tests User CAT Tests
Top Member of the Month
Re: trailing zeros question (logical approach needed) [#permalink] New post 05 Apr 2013, 04:21
Amateur wrote:
Bunuel wrote:
feruz77 wrote:
If p is a natural number and p! ends with y trailing zeros, then the number of zeros that (5p)! ends with will be

a) (p+y) trailing zeros
b) (5p+y) trailing zeros
c) (5p+5y) trailing zeros
d) (p+5y) trailing zeros
e) none of them above

Can someone help me how to solve this question? I think, there must be more than one solution method.


Given: p! has y trailing zeros: \frac{p}{5}+\frac{p}{5^2}+\frac{p}{5^3}+...=y (check for theory on this topic: everything-about-factorials-on-the-gmat-85592.html) --> now, # of trailing zeros for (5p)! will be \frac{5p}{5}+\frac{5p}{5^2}+\frac{5p}{5^3}+...=p+(\frac{5p}{5}+\frac{5p}{5^2}+...)=p+y.

Answer: A.
Hello Bunuel.... There is a typo in the equation just before putting down p+y... others may get confused....


Thank you. Edited. +1.
_________________

PLEASE READ AND FOLLOW: 11 Rules for Posting!!!

RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory

COLLECTION OF QUESTIONS:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. NEW!!!

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS ; 9 Devil's Dozen!!!; 10 Number Properties set. NEW!!!


What are GMAT Club Tests?
25 extra-hard Quant Tests

Find out what's new at GMAT Club - latest features and updates

Re: trailing zeros question (logical approach needed)   [#permalink] 05 Apr 2013, 04:21
    Similar topics Author Replies Last post
Similar
Topics:
 New posts IneqP) If x and y are non-zero integers and |x| + |y| = 32, amitdgr 3 29 Oct 2008, 00:30
New posts 1 If N and P denote the non-zero digits of a four-digit number vscid 3 11 Jan 2009, 18:09
New posts 10 EXPERTS_POSTS_IN_THIS_TOPIC Find the number of trailing zeros in the product of (1^1)*(5 feruz77 9 25 Jan 2011, 06:42
Popular new posts 19 EXPERTS_POSTS_IN_THIS_TOPIC Find the number of trailing zeros in the expansion of feruz77 18 25 Jan 2011, 06:48
New posts 7 EXPERTS_POSTS_IN_THIS_TOPIC If a natural number ‘p’ has 8 factors, then which of the fol kingb 5 11 Nov 2012, 11:30
Display posts from previous: Sort by

If p is a natural number and p! ends with y trailing zeros

  Question banks Downloads My Bookmarks Reviews  
Print view
First unread post

Moderators: Bunuel, VeritasPrepKarishma, IanStewart

Search for:


GMAT Club MBA Forum Home| About| Privacy Policy| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group and phpBB SEO

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.

Main navigation

GMAT Resources

Partners

MBA Resources

www.gmac.com|www.mba.com