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GRE Prep Club Team Member
Joined: 20 Feb 2017
Posts: 2506
Given Kudos: 1055
GPA: 3.39
The function F is defined for all positive integers n by the following
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05 Nov 2021, 07:39
05 Nov 2021, 07:39
Expert Reply
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Question Stats:
25% (01:11) correct
75% (01:50) wrong based on 8 sessions
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The function F is defined for all positive integers n by the following rule: f(n) is the number of positive integer each of which is less than n, and has no positive factor in common with n other than 1. If p is any prime number then f(p)=
A. p-1
B. p-2
C. (p+1)/2
D. (p-1)/2
E. 2
A. p-1
B. p-2
C. (p+1)/2
D. (p-1)/2
E. 2
Re: The function F is defined for all positive integers n by the following
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08 Nov 2021, 14:07
08 Nov 2021, 14:07
Expert Reply
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.
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.
gmatclubot
Re: The function F is defined for all positive integers n by the following [#permalink]
08 Nov 2021, 14:07
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