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

Redeem

Number properties

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Source: — Data Sufficiency |
User avatar
Legendary Member
Posts: 2134
Joined: Mon Oct 20, 2008 11:26 pm
Thanked: 237 times
Followed by:25 members
GMAT Score:730

Re: Number properties

by logitech » Sun Jan 11, 2009 1:33 am
4meonly wrote:Is a/b an integer?

(1) 4a/b is an integer

4(a/b) is integer

if it is 4, a/b = integer

if it is 5 , a/b is not an integer

INSUF


(2) 4b/a is an integer

if b/a = 1, 4b/a is an integer and a/b is an integer

if b/a is 2 , 4b/1 is an integer but a/b is not! (1/2)

(1+2)

a = 4 b = 8

4a/b = integer

4b/a = integer

a/b is not an integer

I learned this method from Cramya :)
LGTCH
---------------------
"DON'T LET ANYONE STEAL YOUR DREAM!"
Top
Legendary Member
Posts: 1169
Joined: Sun Jul 06, 2008 2:34 am
Thanked: 25 times
Followed by:1 members

by aj5105 » Sun Jan 11, 2009 2:00 am
I got C as the answer.

Cramya,
could you please explain taking both together?

thanks!
Top
Legendary Member
Posts: 1169
Joined: Sun Jul 06, 2008 2:34 am
Thanked: 25 times
Followed by:1 members

by aj5105 » Sun Jan 11, 2009 2:06 am
got it :)
aj5105 wrote:I got C as the answer.

Cramya,
could you please explain taking both together?

thanks!
Top
Legendary Member
Posts: 2467
Joined: Thu Aug 28, 2008 6:14 pm
Thanked: 331 times
Followed by:11 members

by cramya » Sun Jan 11, 2009 3:56 am
4a/b and 4b/a are integers and a/b is integer if a=6 and b=3


To prove insufficiency

Take a=2 b=4 for stmt I and stmt II a/b not an integer


Together

Again take a=2 b=4 a/b not integer
Take a=6 b=3 a/b integer

Hence E)
Top
Legendary Member
Posts: 891
Joined: Sat Aug 16, 2008 4:21 am
Thanked: 27 times
Followed by:1 members
GMAT Score:660(

by 4meonly » Thu Jan 15, 2009 7:05 am
Are there any methods without plugin numbers?
Algebraic?
Top
User avatar
Legendary Member
Posts: 2134
Joined: Mon Oct 20, 2008 11:26 pm
Thanked: 237 times
Followed by:25 members
GMAT Score:730

by logitech » Thu Jan 15, 2009 11:13 am
4meonly wrote:Are there any methods without plugin numbers?
Algebraic?
Is a/b an integer?

(1) 4a/b is an integer

a/b=x

4X=K

X=K/4

If K is divisible with 4, X is integer
If not X is not an integer

(2) 4b/a is an integer

4/X=K

X=4/K

If 4 is divisible with K , X is integer if NOT it is not

Together

4/K=K/4

If K is 4 they X is integer

If K is not 4, X is not an integer
LGTCH
---------------------
"DON'T LET ANYONE STEAL YOUR DREAM!"
Top
Post new topic Post Reply
• Page 1 of 1