If x is a prime number, what is the value of x?
(1) x < 15
(2) (x-2) is a multiple of 5
OA: E
Where did I go wrong? :
(1) x could be 2, 3, 5, etc... NOT SUFF
(2) (x-2) = 5k
x= 5k + 2
x could be 7, 17, 37, etc... NOT SUFF
Both together: X=7 because it's the only one less than 15, so C?
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what is the value of x?
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revoltangel
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cramya
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Prime numbers are always positive. I dont think we classify -3,-5,-2 as primesthink on the negative side....
even -3 is a prime number and (x-2) = (-5) is a multiple of 5...
hence, E
Putting k=0 is what u may have missed.
(2) (x-2) = 5k
x= 5k + 2
x could be 7, 17, 37, etc... NOT SUFF
As Vikz very rightly said both 2 and 7 satisfy the 2 statements togetherA silly doubt, but is 0 a possible multiple of 5?
Then 2 also satisfies the condition
2-2 = 0 multiple of 5 (We almost always forget that 0 is a multiple of evry number in DS multiples concept problems).
7-2 = 5 is also a multiple of 5
Hence E)
Is this a problem from the Kaplan free full length exam? I remember seeing something like this.
Hope this helps!
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revoltangel
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Yes it is! Thanks for your help--I did not think of 0 as a multiple.cramya wrote: Is this a problem from the Kaplan free full length exam? I remember seeing something like this.
Hope this helps!
cramya wrote:Prime numbers are always positive. I dont think we classify -3,-5,-2 as primes
yup, your right....
came across an old thread about this also, where Stacey and Ian have commented confirming this.
