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The function f is defined for all positive integers n by the [#permalink]

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06 May 2006, 13:24

This topic is locked. If you want to discuss this question please re-post it in the respective forum.

The function f is defined for all 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 is any prime number then f(p) =

a)p-1
b)p-2
c)(p+1)/2
d)(p-1)/2
e)2

Please explain your answer . I got this one wrong .

i agree with what u have mentioned , but the question is whether to take 1 in the answer or not .

It seems that GMATPREP has taken 1 in account so the answer is P-1 .

I'm confused not for this question but what to do during the real test if i encounter one of this kind

i donot see any reason for p-2 as answer because it isnot mentioned that 1 has to be excluded. 1 is treated as a positive common factor factor not as an integer that is to be excluded. so we should include 1 as well.

therefore, it is p-1.

ipc302 wrote:

The function f is defined for all 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 is any prime number then f(p) =

a)p-1 b)p-2 c)(p+1)/2 d)(p-1)/2 e)2

Please explain your answer . I got this one wrong .

i guess i did this one earlier............................................. a. f(p) = p-1

Prof would you please elaborate your answer. 'cuase I do not know how to solve such kind of questions? Thank you.

Prof when you be back please share your knowledges with me.

M8, sorry i didn't notice your posts.

lets go by example. say 7 is a prime integer. 7 has 1 and 7 as its +ve factors. f (p) = 6, 5, 4, 3, 2, and 1, altogather 6 integers = p-1 = 7-1. it canot be 0 and -ves cuz the question clearly says that any +ve integers.