prime number

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prime number

by kanha81 » Mon Mar 02, 2009 11:47 am
q: If x is a prime number greater than 2, which of following is a prime number?
a) x^2
b) x/2
c) 3x
d) x-4
e) x^2+1
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Re: prime number

by marcusking » Mon Mar 02, 2009 12:01 pm
kanha81 wrote:q: If x is a prime number greater than 2, which of following is a prime number?
a) x^2
b) x/2
c) 3x
d) x-4
e) x^2+1
Not sure there is an answer to this that is always true.

a) If a prime number is squared it is divisible by itself so it's no longer prime
b) A prime number > 2 divided by 2 leaves a fraction which isn't a prime number.
c) any prime number multipled by 3 can also be divided by 3 making it not a prime number
d) 29 is prime 29-4 is 25 (not prime)
e)5^2 = 25. 25 + 1 = 26 (not prime)

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Re: prime number

by piyush_nitt » Tue Mar 03, 2009 4:38 am
kanha81 wrote:q: If x is a prime number greater than 2, which of following is a prime number?
a) x^2
b) x/2
c) 3x
d) x-4
e) x^2+1
IMO D

x=7

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Re: prime number

by kamu » Tue Mar 03, 2009 4:59 am
kanha81 wrote:q: If x is a prime number greater than 2, which of following is a prime number?
a) x^2
b) x/2
c) 3x
d) x-4
e) x^2+1
incorrect question i guess!

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by abhijeetsinghai » Sat Mar 07, 2009 1:02 pm
Incorrect question....

D is wrong if x= 19, x-4=15, not prime

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Re: prime number

by karmayogi » Sat Mar 07, 2009 1:20 pm
kanha81 wrote:q: If x is a prime number greater than 2, which of following is a prime number?
a) x^2
b) x/2
c) 3x
d) x-4
e) x^2+1
I guess, question has to be "which of following could be a prime numbre?" In that case, D will be the answer.
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