Weird Integer Problem : PS Archive
Check GMAT Club Decision Tracker for the Latest School Decision Releases http://gmatclub.com/AppTrack

 It is currently 23 Jan 2017, 21:05

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# Weird Integer Problem

Author Message
Manager
Joined: 27 Oct 2009
Posts: 149
Location: Montreal
Schools: Harvard, Yale, HEC
Followers: 1

Kudos [?]: 82 [0], given: 18

### Show Tags

14 Nov 2009, 19:05
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions

### HideShow timer Statistics

This topic is locked. If you want to discuss this question please re-post it in the respective forum.

Attachments

Arithmetic2.jpg [ 65.1 KiB | Viewed 860 times ]

SVP
Joined: 30 Apr 2008
Posts: 1887
Location: Oklahoma City
Schools: Hard Knocks
Followers: 40

Kudos [?]: 571 [1] , given: 32

### Show Tags

14 Nov 2009, 19:30
1
KUDOS
We know that 450 * y will equal a perfect cube, and we're told that n and y are postiive, so we do not have to worry about that.

450 * y = some cube. Break down 450 into primes

3 * 3 * 5 * 5 * 2

So 3 * 3 * 5 * 5 * 2 must equal some cube. We know that if we had three 3's, three 5's and three 2's, then that would be a perfect cube.

so if you let y equal what we are missing to give us three of each, then y must break down into the primes of 3 * 5 * 2 * 2. This is I. If we know that Y breaks doen to 2 * 5 * 2^2, and that is the denominator with y as the numerator, this will equal 1. for the same reason, we know that II and III will not result in integers.

ezinis wrote:
If n and y are positive integers and $$450y = n^3$$, which of the following must be an integer?

I. $$\frac{y}{3 x 2^2 x 5}$$

II. $$\frac{y}{3^2 x 2 x 5}$$

III. $$\frac{y}{3 x 2 x 5^2}$$

a) None

b) I only

c) II only

d) III only

e I, II and III

_________________

------------------------------------
J Allen Morris
**I'm pretty sure I'm right, but then again, I'm just a guy with his head up his a.

GMAT Club Premium Membership - big benefits and savings

VP
Joined: 05 Mar 2008
Posts: 1473
Followers: 11

Kudos [?]: 261 [1] , given: 31

### Show Tags

14 Nov 2009, 19:31
1
KUDOS
ezinis wrote:

450 y = n^3

450 = 3*3*5*5*2

in order for 450 to have a cube root we need 3 of each number of 3*3*3*5*5*5*2*2*2

we already have two 3's and two 5's and one 2

therefore we need one 3, one 5, and 2 twos

or 3 x 5 x 2^2

Manager
Joined: 27 Oct 2009
Posts: 149
Location: Montreal
Schools: Harvard, Yale, HEC
Followers: 1

Kudos [?]: 82 [0], given: 18

### Show Tags

15 Nov 2009, 05:36
Thanks jallenmorris +1 from me
Re: Weird Integer Problem   [#permalink] 15 Nov 2009, 05:36
Display posts from previous: Sort by