Function f(n)

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Function f(n)

by Nigogo » Sat Aug 22, 2009 11:55 pm
GMAT GURUs! Please help me:)
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 any prime number then f(p)=
A. p-1
B. p-2
C. (p+1)/2
D. (p-1)/2
E. 2

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Re: Function f(n)

by arbiter » Sun Aug 23, 2009 12:03 am
Nigogo wrote:GMAT GURUs! Please help me:)
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 any prime number then f(p)=
A. p-1
B. p-2
C. (p+1)/2
D. (p-1)/2
E. 2
let say p=5
then positive integers each of which is less than n and has no positive factor in common with n other than 1

can be 1,2,3,4
hence f(p)=p-1

OA please
arbiter

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by Nigogo » Sun Aug 23, 2009 12:17 am
Thank you!

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by Nigogo » Sun Aug 23, 2009 12:19 am
Here is another one thank u in advance!
For which of the following functions is f(a+b) = f(a) + f(b) for all positive numbers a and b?
f(x)=x2
f(x)=x+1
f(x)=√x
f(x)=2/x
f(x)=-3x
B-)

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by arbiter » Sun Aug 23, 2009 12:50 am
Nigogo wrote:Here is another one thank u in advance!
For which of the following functions is f(a+b) = f(a) + f(b) for all positive numbers a and b?
f(x)=x2
f(x)=x+1
f(x)=√x
f(x)=2/x
f(x)=-3x
B-)
check out https://www.beatthegmat.com/gmat-prep-qu ... 43618.html
arbiter