What is the positive integer n ? (1) The sum of all of the

Question

What is the positive integer n ?

(1) The sum of all of the positive factors of n that are less than n is equal to n
(2) n < 30

Source: MGMAT

trivikram · Answer

would pick E

(1 ) is a huge pool

(2) is too limited

(1) and (2) we get


6 1,2,3
28 1,2,4,7,14

So even C is not right...

E may be the answer

sm176811 · Answer

Where in MGMAT did u get this. I have the Equations/Inq, Number properties book but do not seem to have any such questions!

kook44 · Answer

It's their problem of the week - on their website

gmatacer · Answer

E. Seems like MGMAT is on the roll!! let me order online course today? I think that will be enough right?

vipin7um · Answer

My Answer would be C. For n=28 (1,2,4,7,14).

- Vipin

giddi77 · Answer

GMATacer, I haven't ordered either the MGMAT online couse or their collection of Challenge Qs, but I just go to their website every week and find the Challenge problem of the week. I always mention the source since we don't want to violate any copyright stuff :wink:

My impression is that the MGMAT challenge problems are defenitely harder than the actual exams. So are GMATClub challenges. But the pool of Qs that you get from GMATClub challenges is around 25 Challenges*37Qs = 925. Not sure how many Qs MGMAT challenge series. Moreover GMATClub challenges come in the form of 25 packaged full length Quant tests, with analysis capabilities. If you are looking for an online course for basics(sort of study material), then you can go for MGAMAT. But if you are looking for 700+ level Qs(I can't vouch for that 'coz I haven't taken the test yet), GMATClub challenges are worth it too.

trivikram · Answer

how about 6??

1,2,3 are factors of 6

shevy · Answer

E <img src="{SMILIES_PATH}/icon_wink.gif" alt=":wink:" title="Wink" />

vipin7um · Answer

Yup, that's another n. I missed that.

E it is.

Thanks Vikram.

ccax · Answer

You're right with E since n could be 6 or 28,
but the pool of perfect numbers is by far not
as huge as it might look like.

The first are

6 
28 
496 
8128 
33550336 
8589869056 
137438691328 
2305843008139952128

ccax · Answer

Sorry, but (1) says
The sum of all of the positive factors of n that are less than n is equal to n,
and there is no positive factor of 1 less than 1.

saurabhmalpani · Answer

Sorry I misread the question ..

Yes answer is E. Saurabh Malpani

gmat_crack · Answer

My bet will be on E.

Since there is more than one number, which satisfies the given condition, hence it is E.

What is the positive integer n ? (1) The sum of all of the

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