BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

if a and b are positive even integers, and the least common

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
User avatar
Master | Next Rank: 500 Posts
Posts: 127
Joined: Tue May 13, 2008 12:28 am
Thanked: 2 times
GMAT Score:710

if a and b are positive even integers, and the least common

by airan » Sat Jul 12, 2008 11:21 pm
If a and b are positive even integers, and the least common multiple of a and b is expressed as ab/n, which of the following statements could be false ?

1. n is a factor of both a and b
2. ab/n < ab

3. ab is multiple of 2.

4. ab/n is a multiple of 2.

5. n is a multiple of 4.

OA is 5
Last edited by airan on Mon Jul 14, 2008 12:50 am, edited 1 time in total.
Thanks
Airan
Top
Source: — Problem Solving |
Legendary Member
Posts: 572
Joined: Fri Feb 22, 2008 9:25 am
Thanked: 21 times

by reachac » Sat Jul 12, 2008 11:32 pm
IMO E

Also in B I thot it should be <=
Top
Master | Next Rank: 500 Posts
Posts: 104
Joined: Wed Jun 04, 2008 4:04 pm
Thanked: 6 times

by swati.sug » Sat Jul 12, 2008 11:37 pm
My pick is 5......n is a multiple of 4 need not be true.
All others have to be true.
Top
Newbie | Next Rank: 10 Posts
Posts: 5
Joined: Wed Jan 23, 2008 11:38 am

by vivekverma » Sun Jul 13, 2008 1:14 am
Ans. E - n can be 2 as well...
Top
Legendary Member
Posts: 829
Joined: Mon Jul 07, 2008 10:09 pm
Location: INDIA
Thanked: 84 times
Followed by:3 members

by sudhir3127 » Sun Jul 13, 2008 2:58 am
Answer E.
Top

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 2623
Joined: Mon Jun 02, 2008 3:17 am
Location: Montreal
Thanked: 1090 times
Followed by:355 members
GMAT Score:780

Re: if a and b are positive even integers, and the least com

by Ian Stewart » Sun Jul 13, 2008 8:31 am
airan wrote:If a and b are positive even integers, and the least common multiple of a and b is expressed as ab/n, which of the following statements could be false ?

1. n is a factor of both a and b
2. ab/n < ab

3. ab is multiple of 2.

4. ab/n is a multiple of 2.

5. n is a multiple of 4.
This question is easier if you know that, for any positive integers a and b:

LCM(a,b) * GCD(a,b) = a*b

So LCM(a,b) = ab/GCD(a,b)

In this question, n is just the GCD of a and b. So we know automatically that n is a factor of a and b... A) must be true. If a and b are both even, they are both divisible by 2, so the smallest possible value for their GCD is 2. That is, n >= 2, so B) must be true (I'd add, in response to reachac's comment above, we do not need to have <= here). If a and b are even, ab is clearly even, and so is the LCM of a and b, so C) and D) must be true. E) is the only one that might be false; E will only be true if both a and b are divisible by 4.
For online GMAT math tutoring, or to buy my higher-level Quant books and problem sets, contact me at ianstewartgmat at gmail.com

ianstewartgmat.com
Top
Post new topic Post Reply
• Page 1 of 1