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answer correct? 32

by magical cook » Wed Dec 19, 2007 8:05 am
If n is an integer between 10 and 99, is n < 80 ?
(1) The sum of the two digits of n is a prime number.
(2) Each of the two digits of n is a prime number.




I think B but it says C..
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by StarDust845 » Wed Dec 19, 2007 8:45 am
well there atleast two numbers 32 and 52.

Calista.
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by gabriel » Wed Dec 19, 2007 10:45 am
Hi Magical Cook,

Well, I would say B too, there is no two digit number greater than 80 that has both its integer prime, so n has to be less that 80 .. btw what is the source of the question

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by magical cook » Wed Dec 19, 2007 1:42 pm
Hmm. This is from gmatprep. so, answer should be correct but I dont understand why it's C..
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by samirpandeyit62 » Wed Dec 19, 2007 11:39 pm
I dont see how the ans can be C

If n is an integer between 10 and 99, is n < 80 ?

(2) Each of the two digits of n is a prime number.

for this stmt to be false we need to deduce that both n<80

& n GE (greater than or equal to) 80
are possible

n<80 we have 73

but for n GE (greater than or equal to) 80, we will have values
80-89 (first digit is eight) 90-99 (first digit 9) so none of these numbers would satisfy stmt 2

however is there a possibility that a soln can be incorrect in gmatprep?
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by camitava » Thu Dec 20, 2007 12:44 am
Magical_cook, ur Qs is -
If n is an integer between 10 and 99, is n <80> 80
or = 21, 23, ... When n < 80
So not A or D.
If we go by 2,
n = any prime number at unit's digit with 3, 5 and 7 but neither 8 nor 9 as ten's digit .

Now by this, we can conclude by B that the best option to chose is B. Guys am I correct?
Correct me If I am wrong


Regards,

Amitava
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by rbansal » Mon May 16, 2011 5:33 pm
magical cook wrote:If n is an integer between 10 and 99, is n < 80 ?
(1) The sum of the two digits of n is a prime number.
(2) Each of the two digits of n is a prime number.


The answer for this is B I have the GMAT Prep answer and it is B.



I think B but it says C..
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by jerseyny » Fri May 20, 2011 7:48 pm
wow if the answer is C it means that I have to study a lot more.. I do think its B?

For example, as Each of the two digit needs to be a prime number and 8 and 9 is not a prime, there couldn't be any number which satisfies this condition if the number is bigger than 80... as there will always be one number which is not prime..
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by uslalas22 » Fri May 20, 2011 8:02 pm
Agree as well that it should be B for the reasoning's noted.
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by vineethyoung » Mon Dec 05, 2011 2:21 am
First thing I did was to reframe the question:
10<n<99, is n<80?

For (2) Each of the two digits of n is a prime number:
I listed some #'s that only have prime #'s for each of the two digits, such as, 22, 33, 55, 77, etc. From this I deduced that the largest number n could be is 77, thus n<80. SUFF

For (1) The sum of the two digits of n is a prime number.
This was a little more tedious, I listed all possible combo's in my own short way:
1 1
2 2
3 3
4 4
5 5
6 6
7 7
8 8
9 9

By visualizing this I could use connecting arrows to see what the possibilities are. I could make a combo of a # below 80, such as, if n = 74 -> then 7+4 = 11, a prime number, and thus n<80 (and still maintaining 10<n<99).
Also, I could make a combo of a # greater than 80, such as, if n = 83 -> 8+ 3 = 11, a prime number, and thus n>80. Since we have n<80 and n>80, INSUFF.

Thus answer is B.
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by amit2k9 » Mon Dec 05, 2011 2:48 am
10< n < 99
if both digits are prime.Then 8 and 9 are ruled out.
hence its B.

If its C then something is missing in the question.
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by anikendra » Tue Dec 06, 2011 9:35 am
answer is B as per the answer in gmatprep...
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by [email protected] » Sat Feb 18, 2012 6:22 am
Are you sure Aniket that the answer is B as per the GMAT prep...

though it should be B as we all have solved it but just check all of you guyz once inorder to know wat is the OA...
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