GMAT Question of the Day: Daily via email | Daily via Instagram New to GMAT Club? Watch this Video

It is currently 07 Aug 2020, 11:03

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

If is n is multiple of 5, and n=p^2*q where p and q are prim

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

Hide Tags

Find Similar Topics 
Manager
Manager
avatar
Joined: 23 Jun 2008
Posts: 126
If is n is multiple of 5, and n=p^2*q where p and q are prim  [#permalink]

Show Tags

New post 05 Feb 2010, 11:51
9
127
00:00
A
B
C
D
E

Difficulty:

  45% (medium)

Question Stats:

66% (01:39) correct 34% (01:50) wrong based on 2796 sessions

HideShow timer Statistics

If is n is multiple of 5, and n=p^2*q where p and q are prime, which of the following must be a multiple of 25?

A. p^2
B. q^2
C. pq
D. p^2*q^2
E. p^3*q
Most Helpful Expert Reply
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 65854
Re: GMAT Prep - Prime Number  [#permalink]

Show Tags

New post 05 Feb 2010, 12:11
32
59
If \(n\) is multiple of \(5\), and \(n = p^2q\) where \(p\) and \(q\) are prime, which of the following must be a multiple of \(25\)?

A \(p^2\)
B. \(q^2\)
C. \(pq\)
D. \(p^2q^2\)
E. \(p^3q\)

\(n=5k\) and \(n=p^2p\), (\(p\) and \(q\) are primes).
Q: \(25m=?\)

Well obviously either \(p\) or \(q\) is \(5\). As we are asked to determine which choice MUST be multiple of \(25\), right answer choice must have BOTH, \(p\) and \(q\) in power of 2 or higher to guarantee the divisibility by \(25\). Only D offers this.

Answer: D.
_________________
Most Helpful Community Reply
Manager
Manager
avatar
Joined: 26 May 2005
Posts: 141
Re: GMATPrep  [#permalink]

Show Tags

New post 06 Apr 2010, 21:55
19
9
n is a multiple of 5
n = pq^2 and p and q are primes numbers... so either p or q is 5 or both are 5

A. p^2 -- q could be 5, so this might not be a multiple of 25
B. q^2 -- p could be 5, so this might not be a multiple of 25
C. pq -- p could be 5 and q some other prime number,so this might not be a multiple of 25
D. p^2q^2 -- bingo, either p or q has to be 5, and this one sure will be a multiple of 25
E.p^3q - q could be 5, so this might not be a multiple of 25

D
General Discussion
Manager
Manager
User avatar
Joined: 13 Dec 2009
Posts: 165
Reviews Badge
Re: GMAT Prep - Prime Number  [#permalink]

Show Tags

New post 12 Mar 2010, 05:35
8
1
4
If n is a multiple of 5 and n = p^2*q, where p and q are prime numbers which of the following must be a multiple of 25

n is a multiple of 5 and p and q are prime numbers.
the only prime number which multiple of 5 i s5 itself
so either p or q is 5
This is why we can surely say that p^2*q^2 is the multiple of 25 since one of thme is 5 and 5^2 = 25
so d is the answer
Manager
Manager
avatar
Joined: 24 Jul 2009
Posts: 173
Re: multiples and prime: help please  [#permalink]

Show Tags

New post 18 Apr 2010, 12:43
2
1
MMMs wrote:
Sorry (in advance) if I'm not posting this in the right place. Not sure I quite figured what to post where...
Could someone help me with this question? TIA!

If n is a multiple of 5 and \(n=p^2q\), where p and q are prime numbers, which of the following must be a multiple of 25?
a) \(p^2\)
b) \(q^2\)
c) \(pq\)
d) \(p^2q^2\)
e) \(p^3q\)


IMHO D

if n is a multiple of 5, it means [/m]p^2q[/m]is multiple of 5. Now both p and q are prime, so atleast one of them should be 5.

let say if p=5, then and q=3, (n=75) ,then option b is out. >>> [/m]3^2[/m] is not a multiple of 25.
let say if p=3, then and q=5, (n=45) ,then option a is out. >>> [/m]3^2[/m] is not a multiple of 25.
let say if p=3, then and q=5, (n=45) ,then option c is out. >>> 3 * 5 is not a multiple of 25.
let say if p=3, then and q=5, (n=135) ,then option e is out. >>>[/m]3^3 * 5[/m] is not a multiple of 25.

Let see option D.

Both p or q can be 5, and if any one of them is squared, the result will be divisible by 5...!!
Magoosh GMAT Instructor
User avatar
Affiliations: Magoosh
Joined: 28 Nov 2011
Posts: 33
Location: United States (CA)
Re: no.prop  [#permalink]

Show Tags

New post 19 Dec 2011, 14:43
13
5
For this question, it's best to look at the equation and the conditions together. Here's what we know:
1. n must be a multiple of 5
2. n=p^2*q
3. p and q are prime numbers.

For n to be a multiple of 5, either p or q has to be 5. They can't be 10, 15, 25, etc. since they have to be prime numbers. As long as one of the two is 5, the other can be any prime number. Knowing this, take a look at the answer choices:

A. p^2
B. q^2
C. pq
D.p^2*q^2
E.p^3*q

A and B should be eliminated, because the question asks "which of the following MUST be a multiple of 25", which means for whatever values we put in that fulfill the conditions in the stem, the correct answer choice should be 25. A and B are both at risk of either p or q being the "other" prime number (p=5 and q=3, p=3 and q=5) in which case 9 won't be divisible by 25.

C is also out-- we can finagle p and q into both being 5 to make this true, but it will not be true for every case, since p or q can just as easily be 3, and 15 won't be divisible by 25.

D is the correct answer because regardless of what p or q may be individually, the fact is that one of them will always have to be 5 and thus the result of p^2*q^2 will always be divisible by 25, which is what we're looking for in the correct answer.

E is incorrect because it's actually very similar to C, where we can potentially make it divisible by 25, but it won't be true for every case.

I hope that helps, feel free to let me know if you have any other questions!
_________________
Margarette
Magoosh Test Prep

Image

Image
Manager
Manager
avatar
Joined: 27 Feb 2012
Posts: 111
Re: If n is a multiple of 5 and n=(p^2)q, where p and q are prim  [#permalink]

Show Tags

New post 19 Jan 2013, 02:17
1
kiyo0610 wrote:
If n is a multiple of 5 and n=(p^2)q, where p and q are prime numbers, which of the following must be a multiple of 25 ?

(a)p^2
(b)q^2
(c)pq
(d)(p^2)(q^2)
(e)(p^3)q


either p = 5 or q = 5
Simply go to options
a) p = 2 say and q = 5
b) q =2 and p = 5
c) p =2 and q =5
d) either of p or q is 5 so this will be multiple of 25
e) p = 2 and q =5


So only D stands
Senior Manager
Senior Manager
avatar
B
Joined: 24 Aug 2009
Posts: 427
Schools: Harvard, Columbia, Stern, Booth, LSB,
Re: if n is a multiple of 5 ...  [#permalink]

Show Tags

New post 24 Jul 2013, 17:26
2
if n is a multiple of 5 and n=P^2q,where p and g are prime numbers, which of the following must be a multiple of 25?
a. p^2 - q can be a multiple of 25

b. q^2 - - P can be a multiple of 25

c. pq - PQ is definitely a multiple of 5 but it not necessarily a multiple of 25

d. (P^2)(q^2) - Correct

e. (P^3)(q) - Assuming the worst case scenario (P is some other prime number except 5), Q is definitely a multiple of 5 but it not necessarily a multiple of 25
Intern
Intern
avatar
Joined: 17 Jul 2013
Posts: 47
GMAT 1: 710 Q49 V38
GRE 1: Q166 V160
GPA: 3.74
Re: If is n is multiple of 5, and n=p^2*q where p and q are prim  [#permalink]

Show Tags

New post 27 Aug 2014, 03:39
My question is that what if n in the following question stem is equal to p^(2q), instead of (p^2)(q). how would the answer change.... My reasoning goes like this:

Since p raised to some integer power means p.p.p.p..... up to 2q. (1) and since (1) is divisible by 5, p must be divisible by 5. Hence, p^2 must be divisible by 25. Is this reasoning correct?
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 65854
Re: If is n is multiple of 5, and n=p^2*q where p and q are prim  [#permalink]

Show Tags

New post 27 Aug 2014, 04:12
megatron13 wrote:
If \(n\) is multiple of \(5\), and \(n = p^2q\) where \(p\) and \(q\) are prime, which of the following must be a multiple of \(25\)?

A \(p^2\)
B. \(q^2\)
C. \(pq\)
D. \(p^2q^2\)
E. \(p^3q\)

My question is that what if n in the following question stem is equal to p^(2q), instead of (p^2)(q). how would the answer change.... My reasoning goes like this:

Since p raised to some integer power means p.p.p.p..... up to 2q. (1) and since (1) is divisible by 5, p must be divisible by 5. Hence, p^2 must be divisible by 25. Is this reasoning correct?


Yes, if we were told that p^(2q) is a multiple of 5 where p and q are primes, then p must be 5, which will guarantee divisibility by 25 of each option but B (q^2) and C (pq).
_________________
Director
Director
User avatar
B
Joined: 03 Feb 2013
Posts: 838
Location: India
Concentration: Operations, Strategy
GMAT 1: 760 Q49 V44
GPA: 3.88
WE: Engineering (Computer Software)
Reviews Badge
If is n is multiple of 5, and n=p^2*q where p and q are prime, w  [#permalink]

Show Tags

New post 20 Dec 2014, 09:49
Lets say p^2 * q = 5
Then only q^2 and p^2 *q^2 can be 25 -> All other options are eliminated.
Lets say p^2 * q = 25
then q^2 is eliminated.
Hence D)
Current Student
User avatar
B
Joined: 20 Jan 2017
Posts: 48
Location: United States (NY)
Schools: CBS '20 (A)
GMAT 1: 750 Q48 V44
GMAT 2: 610 Q34 V41
GPA: 3.92
Reviews Badge
Re: If is n is multiple of 5, and n=p^2*q where p and q are prim  [#permalink]

Show Tags

New post 26 Jan 2017, 15:47
1) Since n consists of two prime numbers p and q and it divisible by 5, either p or q have to be 5.
2) If we square both p and q, and one of them is 5, the product will have to be divisible by 5^2=25.

The correct answer is D.
Director
Director
avatar
G
Joined: 02 Sep 2016
Posts: 620
Re: If is n is multiple of 5, and n=p^2*q where p and q are prim  [#permalink]

Show Tags

New post 03 Apr 2017, 09:21
n is of the form 5a where a is any positive integer.
p or q is 5, otherwise n cannot be a multiple of 5.
So to be sure that the answer is a multiple of 25, p^2q^2 is the right answer. For example, if p=5 then p^2 will be a multiple of 25 and same for q.
Manager
Manager
avatar
B
Joined: 02 Jan 2017
Posts: 66
Location: Pakistan
Concentration: Finance, Technology
GMAT 1: 650 Q47 V34
GPA: 3.41
WE: Business Development (Accounting)
Reviews Badge
Re: If is n is multiple of 5, and n=p^2*q where p and q are prim  [#permalink]

Show Tags

New post 11 Dec 2017, 03:26
Bunuel wrote:
If \(n\) is multiple of \(5\), and \(n = p^2q\) where \(p\) and \(q\) are prime, which of the following must be a multiple of \(25\)?

A \(p^2\)
B. \(q^2\)
C. \(pq\)
D. \(p^2q^2\)
E. \(p^3q\)

\(n=5k\) and \(n=p^2p\), (\(p\) and \(q\) are primes).
Q: \(25m=?\)

Well obviously either \(p\) or \(q\) is \(5\). As we are asked to determine which choice MUST be multiple of \(25\), right answer choice must have BOTH, \(p\) and \(q\) in power of 2 or higher to guarantee the divisibility by \(25\). Only D offers this.

Answer: D.




Can this be done with this approach, that prime factors of a perfect square will have even powers? By this theory, only D option meets the criteria. Correct me if I am wrong.
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 65854
Re: If is n is multiple of 5, and n=p^2*q where p and q are prim  [#permalink]

Show Tags

New post 11 Dec 2017, 03:53
mtk10 wrote:
Bunuel wrote:
If \(n\) is multiple of \(5\), and \(n = p^2q\) where \(p\) and \(q\) are prime, which of the following must be a multiple of \(25\)?

A \(p^2\)
B. \(q^2\)
C. \(pq\)
D. \(p^2q^2\)
E. \(p^3q\)

\(n=5k\) and \(n=p^2p\), (\(p\) and \(q\) are primes).
Q: \(25m=?\)

Well obviously either \(p\) or \(q\) is \(5\). As we are asked to determine which choice MUST be multiple of \(25\), right answer choice must have BOTH, \(p\) and \(q\) in power of 2 or higher to guarantee the divisibility by \(25\). Only D offers this.

Answer: D.




Can this be done with this approach, that prime factors of a perfect square will have even powers? By this theory, only D option meets the criteria. Correct me if I am wrong.


A multiple of 25 is not necessarily a perfect square. For example, 75 is a multiple of 25 but is not a perfect square.
_________________
Target Test Prep Representative
User avatar
V
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 11419
Location: United States (CA)
Re: If is n is multiple of 5, and n=p^2*q where p and q are prim  [#permalink]

Show Tags

New post 12 Dec 2017, 07:06
1
1
balboa wrote:
If is n is multiple of 5, and n=p^2*q where p and q are prime, which of the following must be a multiple of 25?

A. p^2
B. q^2
C. pq
D. p^2*q^2
E. p^3*q


A common phrase that is used on the GMAT is the word must. In this question, we are asked which of the following must be a multiple of 25. This means that one of our answer choices will always be a multiple of 25, no matter what. It is our job to determine which one, based on the given information.

We are given that n is a multiple of 5, n = (p^2)q, and that p and q are prime numbers.

Because n is a multiple of 5, a prime number, we know that either p or q is 5. Let’s now analyze each answer choice to determine which one MUST (in all cases) be a multiple of 25.

A) p^2

If p = 3, then p^2 = 9 is not a multiple of 25. Answer choice A is not correct.

B) q^2

If q = 3, then q^2 = 9 is not a multiple of 25. Answer choice B is not correct.


C) pq

If p = 5 and q = 3 (or vice versa), pq = 15 is not a multiple of 25. Answer choice C is not correct.

D) (p^2)(q^2)

Regardless of which values we select for p and q, since we know that either p or q is 5, (p^2)(q^2) will always be a multiple of 25. If this is too difficult to see, let’s use numbers.

If p = 5 and q = 3, (p^2)(q^2) = (25)(9) is a multiple of 25.

If p = 3 and q = 5, (p^2)(q^2) = (9)(25) is also a multiple of 25.

Answer choice D is correct.

For practice, let’s analyze answer choice E.

E) (p^3)q

If p = 3 and q = 5, then (p^3)q = 135 is not a multiple of 25. Answer choice E is not correct.

Answer: D
_________________

  250 REVIEWS

5-STAR RATED ONLINE GMAT QUANT SELF STUDY COURSE

NOW WITH GMAT VERBAL (BETA)

See why Target Test Prep is the top rated GMAT quant course on GMAT Club. Read Our Reviews

EMPOWERgmat Instructor
User avatar
V
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 17292
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: Q170 V170
Re: If is n is multiple of 5, and n=p^2*q where p and q are prim  [#permalink]

Show Tags

New post 16 Jan 2018, 12:36
Hi All,

This question is built around a couple of Number Properties and can be solved by TESTing VALUES.

To start, we're told two things about N...
1) N is a multiple of 5
2) N = (P)(P)(Q)

Since N is a multiple of 5, at least one of it's prime factors MUST be a 5. We're told that P and Q are both PRIME, which means that P or Q or both will be a multiple of 5. This is an interesting point, since the question asks which of the following MUST be a multiple of 25 (meaning - which of these answers will ALWAYS be a multiple of 25 no matter how many different examples you can come up with?). As such, we will have to consider a couple of different possibilities...

IF...
P = 5
Q = 2
N = 50
We can eliminate answers B and C.

IF....
P = 2
Q = 5
N = 20
We can eliminate answers A and E.

Final Answer:

GMAT assassins aren't born, they're made,
Rich
_________________
Contact Rich at: Rich.C@empowergmat.com
Image


The Course Used By GMAT Club Moderators To Earn 750+

souvik101990 Score: 760 Q50 V42 ★★★★★
ENGRTOMBA2018 Score: 750 Q49 V44 ★★★★★
Non-Human User
User avatar
Joined: 09 Sep 2013
Posts: 15637
Re: If n is a multiple of 5 and n=p^2 *q, where p and q are  [#permalink]

Show Tags

New post 07 Oct 2019, 02:44
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
GMAT Club Bot
Re: If n is a multiple of 5 and n=p^2 *q, where p and q are   [#permalink] 07 Oct 2019, 02:44

If is n is multiple of 5, and n=p^2*q where p and q are prim

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





cron

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