the function f(n) : GMAT Problem Solving (PS)

the function f(n)

Oldest

Best Reply

Author

Message

TAGS:

Manager

Joined: 07 Feb 2010

Posts: 170

Followers: 1

Kudos [?]: 21 [0], given: 101

the function f(n) [#permalink]

28 Oct 2010, 08:27

00:00

Question Stats:

63% (01:46) correct

36% (00:53) wrong

based on 0 sessions

the function f is defined for all the positive integers n by the following rule: f(n) is the number of positive integers each of which is less than n and has no positive factor in common with n other than 1 . if p is a prime number then f(p)?
a p-1
b p-2
c (p+1)/2
d (p-1)/2
e 2

please provide ur answer with explanation

[Reveal] Spoiler: OA

GMAT Club team member

Joined: 02 Sep 2009

Posts: 11518

Followers: 1792

Kudos [?]: 9538 [0], given: 826

Re: the function f(n) [#permalink]

28 Oct 2010, 08:31

anilnandyala wrote:

The confusing moment in this question is its wording. Basically question is: how many positive integers are less than given prime number p which has no common factor with p except 1.

Well as p is a prime, all positive numbers less than p have no common factors with p (except common factor 1). So there would be p-1 such numbers (as we are looking number of integers less than p).

If we consider p=7 how many numbers are less than 7 having no common factors with 7: 1, 2, 3, 4, 5, 6 --> 7-1=6.

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

Joined: 01 Nov 2010

Posts: 185

Location: Zürich, Switzerland

Followers: 2

Kudos [?]: 11 [0], given: 20

Re: the function f(n) [#permalink]

09 Nov 2010, 07:46

The moment you put a prime number in the function f(n), notice that all the numbers lesser than n have no divisor clashing with divisor of n since n is prime!!.

For instance f(7)= {6, 5, 4, 3, 2, 1}

Thus for f(p) number of integers falling under this set will be p-1

Answer :- A

Re: the function f(n) [#permalink] 09 Nov 2010, 07:46

		Similar topics	Author	Replies	Last post
Similar Topics:		When n = 100x + 10y + z, function f is defined as f(n) =	gamjatang	7	06 Dec 2005, 07:56
		When n = 100x + 10y + z, function f is defined as f(n) =	MA	1	22 Jun 2006, 21:46
	1	When n = 100x + 10y + z, function f is defined as f(n) =	young_gun	2	22 Apr 2008, 16:17
		The function f(n) = the number of factors of n. If p and q	selvae	4	05 Dec 2008, 20:30
	1	The function F(n) is defined as the product of all the conse	thevenus	2	15 Oct 2012, 11:16

the function f(n)

Main navigation

GMAT Resources

Partners

MBA Resources

GMAT ® is a registered trademark of the Graduate Management Admission Council ® (GMAC ®). GMAT Club's website has not been reviewed or endorsed by GMAC.

GMAT Courses

Admissions Consulting

the function f(n)

the function f(n)

Main navigation

GMAT Resources

Partners

MBA Resources