Hey.. I made the same mistake as well and chose "None" in the test.
But i guess you can also look at it this way:-
450 y = n^3; (3*3*5*5*2)*y = n^3; Therefore y = (n^3) / (3*3*5*5*2)
Option I --> y / (3*2*2*5) --> n^3 / (3*3*3*2*2*2*5*5*5)
Note the denominator of n^3 now has integers 3, 2 and 5 all with powers of 3. That makes n^3 an integer.
Try this with Options 2 and 3 - but you won't end up with cubes in the denominator. That's why the Answer is (I).
Plz correct me if i'm wrong!
please help GmapPrep question
This topic has expert replies
Source: Beat The GMAT — Problem Solving |
-
pepeprepa
- Legendary Member
- Posts: 661
- Joined: Tue Jul 08, 2008 12:58 pm
- Location: France
- Thanked: 48 times
arch I think the thing you should add to your reasoning is that n has at least 2.3.5 among its factors.
Because with 1) we arrive at (n/2*3*5)^3
This is not an integer if n=10 for example. n at least has 2*3*5 among its factors and we know that thanks to y*450=n^3
Because with 1) we arrive at (n/2*3*5)^3
This is not an integer if n=10 for example. n at least has 2*3*5 among its factors and we know that thanks to y*450=n^3
GMAT/MBA Expert
-
Ian Stewart
- GMAT Instructor
- Posts: 2623
- Joined: Mon Jun 02, 2008 3:17 am
- Location: Montreal
- Thanked: 1090 times
- Followed by:355 members
- GMAT Score:780
The answer is B, not E.
I posted a solution to this problem here:
www.beatthegmat.com/number-properties-q-t13973.html
You must have multiplied incorrectly; 15^3, an odd number, cannot be equal to 450*2 = 900, which is even.drgmatIL wrote:I found that N = 15,y=2
where I'm wrong?
I posted a solution to this problem here:
www.beatthegmat.com/number-properties-q-t13973.html
Ian Stewart wrote:The answer is B, not E.
You must have multiplied incorrectly; 15^3, an odd number, cannot be equal to 450*2 = 900, which is even.drgmatIL wrote:I found that N = 15,y=2
where I'm wrong?
I posted a solution to this problem here:
www.beatthegmat.com/number-properties-q-t13973.html
The answer is B Indeed, i was wrong, did not pay too much attention....thanks
