|
Author |
Message |
|
TAGS:
|
|
|
Manager
Joined: 23 Jan 2008
Posts: 115
Followers: 1
Kudos [?]:
12
[2] , given: 0
|
If n=4p, where p is a prime number greater than 2, how many [#permalink]
 23 Jan 2008, 12:07
2
This post received
KUDOS
If n=4p, where p is a prime number greater than 2, how many different positive even divisors does n have, including n?
A. 2
B. 3
C. 4
D. 6
E. 8
Last edited by blog on 23 Jan 2008, 12:41, edited 1 time in total.
|
|
|
|
|
|
|
CEO
Joined: 17 Nov 2007
Posts: 3596
Concentration: Entrepreneurship, Other
Schools: Chicago (Booth) - Class of 2011
GMAT 1: 750 Q50 V40
Followers: 231
Kudos [?]:
1300
[0], given: 346
|
Dn=4p=2^2*p N=(2+1)(1+1)=6
_________________
iOS/Android: GMAT ToolKit - The bestselling GMAT prep app | GMAT Club (free) | PrepGame | GRE ToolKit | LSAT ToolKit
PROMO: Are you an exiting GMAT ToolKit (iOS) user? Get GMAT ToolKit 2 (iOS) for only $0.99 (read more)
Math: GMAT Math Book ||| General: GMATTimer ||| Chicago Booth: Slide Presentation
The People Who Are Crazy Enough to Think They Can Change the World, Are the Ones Who Do.
|
|
|
|
|
|
Manager
Joined: 23 Jan 2008
Posts: 115
Followers: 1
Kudos [?]:
12
[0], given: 0
|
walker wrote: D
n=4p=2^2*p
N=(2+1)(1+1)=6 Quote: oops m sorry its : where p is a prime no greater than 2 here in the question.
|
|
|
|
|
|
Director
Joined: 01 Jan 2008
Posts: 635
Followers: 3
Kudos [?]:
114
[0], given: 1
|
The answer is A. The even divisors are 2*p and 4*p. There are two more divisors 1 and p but they are odd since p > 2
|
|
|
|
|
|
Senior Manager
Joined: 15 Aug 2007
Posts: 257
Schools: Chicago Booth
Followers: 1
Kudos [?]:
36
[0], given: 0
|
My pick B (3)
Even divisors - 2, 4, and n (n will be even after multiplying with 4)
|
|
|
|
|
|
Manager
Joined: 23 Jan 2008
Posts: 115
Followers: 1
Kudos [?]:
12
[0], given: 0
|
maratikus wrote: The answer is A. The even divisors are 2*p and 4*p. There are two more divisors 1 and p but they are odd since p > 2 but here ans is C.
|
|
|
|
|
|
CEO
Joined: 17 Nov 2007
Posts: 3596
Concentration: Entrepreneurship, Other
Schools: Chicago (Booth) - Class of 2011
GMAT 1: 750 Q50 V40
Followers: 231
Kudos [?]:
1300
[0], given: 346
|
maratikus wrote: The answer is A. The even divisors are 2*p and 4*p. There are two more divisors 1 and p but they are odd since p > 2 I lose " even"... I should go to sleep....bye-bye! 
_________________
iOS/Android: GMAT ToolKit - The bestselling GMAT prep app | GMAT Club (free) | PrepGame | GRE ToolKit | LSAT ToolKit
PROMO: Are you an exiting GMAT ToolKit (iOS) user? Get GMAT ToolKit 2 (iOS) for only $0.99 (read more)
Math: GMAT Math Book ||| General: GMATTimer ||| Chicago Booth: Slide Presentation
The People Who Are Crazy Enough to Think They Can Change the World, Are the Ones Who Do.
|
|
|
|
|
|
Senior Manager
Joined: 15 Aug 2007
Posts: 257
Schools: Chicago Booth
Followers: 1
Kudos [?]:
36
[0], given: 0
|
What am I thinking, of course the anser is C:
2, 4, 2*p, and 4*p.
Last two are even numbers too.
|
|
|
|
|
|
Director
Joined: 01 Jan 2008
Posts: 635
Followers: 3
Kudos [?]:
114
[1] , given: 1
|
1
This post received
KUDOS
that's funny, I totally messed up too - concentration is important.
|
|
|
|
|
|
CEO
Joined: 21 Jan 2007
Posts: 2797
Location: New York City
Followers: 5
Kudos [?]:
132
[0], given: 4
|
blog wrote: If n=4p, where p is a prime number greater than 2, how many different positive even divisors does n have, including n?
A. 2
B. 3
C. 4
D. 6
E. 8 i plugged an easy number. n=4p n =4*3 n =12 12 = 2^2 * 3 (2+1)(1+1) = total 3*2=6 total - odd = even 6 - (2)= 4
_________________
You tried your best and you failed miserably. The lesson is 'never try'. -Homer Simpson
|
|
|
|
|
|
Director
Joined: 12 Jul 2007
Posts: 875
Followers: 8
Kudos [?]:
135
[1] , given: 0
|
1
This post received
KUDOS
I agree with BMW here, why not plug in the easiest numbers you can find? What works in one situation will work for the problem.
|
|
|
|
|
|
SVP
Joined: 28 Dec 2005
Posts: 1612
Followers: 1
Kudos [?]:
53
[0], given: 2
|
dont overcomplicate things, just pick numbers  n=12,20,28,40... youll see that each of these numbers have 4 even divisors.
|
|
|
|
|
|
Senior Manager
Joined: 26 Jan 2008
Posts: 267
Followers: 2
Kudos [?]:
58
[0], given: 1
|
blog wrote: If n=4p, where p is a prime number greater than 2, how many different positive even divisors does n have, including n?
A. 2
B. 3
C. 4
D. 6
E. 8 (C) 4*p = 2*2*p Hence, 4 even divisors: 2, 4, 2*p, 4*p
_________________
My GMAT debrief
|
|
|
|
|
|
CEO
Joined: 29 Aug 2007
Posts: 2530
Followers: 41
Kudos [?]:
358
[0], given: 19
|
|
|
|
|
|
|
Senior Manager
Joined: 20 Dec 2004
Posts: 268
Followers: 6
Kudos [?]:
43
[0], given: 0
|
GMAT TIGER wrote: walker wrote: D
n=4p=2^2*p
N=(2+1)(1+1)=6 nice formulae to remember. What is the rule for this formula.. ?
_________________
Stay Hungry, Stay Foolish
|
|
|
|
|
|
Manager
Joined: 02 Jan 2008
Posts: 162
Followers: 1
Kudos [?]:
34
[1] , given: 0
|
1
This post received
KUDOS
neelesh wrote:
What is the rule for this formula.. ?
Number of divisors of N = (m+1)(n+1)(p+1)... Where, N = (a^m)(b^n)(c^p)..and a,b,c.. are prime numbers example, 24 = 2^3*3^1; number of divisors = (3+1)(1+1)=8 (1,24,2,4,6,8,3,12)
|
|
|
|
|
|
CEO
Joined: 17 Nov 2007
Posts: 3596
Concentration: Entrepreneurship, Other
Schools: Chicago (Booth) - Class of 2011
GMAT 1: 750 Q50 V40
Followers: 231
Kudos [?]:
1300
[1] , given: 346
|
1
This post received
KUDOS
neelesh wrote: What is the rule for this formula.. ? for positive integer n=p_1^a*p_2^b...p_m^k, where p_i - are prime numbers The number of positive factors is: N=(a+1)(b+1)....(k+1)
_________________
iOS/Android: GMAT ToolKit - The bestselling GMAT prep app | GMAT Club (free) | PrepGame | GRE ToolKit | LSAT ToolKit
PROMO: Are you an exiting GMAT ToolKit (iOS) user? Get GMAT ToolKit 2 (iOS) for only $0.99 (read more)
Math: GMAT Math Book ||| General: GMATTimer ||| Chicago Booth: Slide Presentation
The People Who Are Crazy Enough to Think They Can Change the World, Are the Ones Who Do.
|
|
|
|
|
|
Manager
Joined: 07 Jan 2008
Posts: 114
Followers: 1
Kudos [?]:
16
[0], given: 0
|
what a great formula!!!! that itself will improve my score 
|
|
|
|
|
|
Senior Manager
Joined: 20 Dec 2004
Posts: 268
Followers: 6
Kudos [?]:
43
[0], given: 0
|
+1 to both walker and srp. thx.
_________________
Stay Hungry, Stay Foolish
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Similar topics |
Author |
Replies |
Last post |
|
Similar
Topics:
|
 |
|
|
If n = 4p, where p is a prime number greater than 2 how many
|
Priti |
8 |
14 Aug 2005, 13:43 |
|
|
|
|
If n=4p, where p is a prime number greater than 2, how many
|
cucrose |
8 |
16 Jan 2007, 11:31 |
|
|
|
|
If n=4p, where p is a prime number greater than2, how many
|
iamba |
3 |
24 Jun 2007, 21:21 |
|
|
|
|
If n=4p, where p is a prime number greater than 2. How many
|
empanado |
1 |
30 Jun 2007, 20:29 |
|
|
8
|
|
If n=4p where p is a prime number greater than 2, how many
|
tinman1412 |
7 |
24 Aug 2007, 09:41 |
|
|
|
|
|
|
close
