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

Redeem

modulo le

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Legendary Member
Posts: 1578
Joined: Sun Dec 28, 2008 1:49 am
Thanked: 82 times
Followed by:9 members
GMAT Score:720

modulo le

by maihuna » Tue Mar 15, 2011 12:15 pm
If a and b are positive integers and a > b, what is the remainder
when a2 -2ab + b2 is divided by 9 ?
(1) The remainder when a - b is divided by 3 is 2.
(2) The remainder when a - b is divided by 9 is 2.
Charged up again to beat the beast :)
Top
Source: — Data Sufficiency |
Legendary Member
Posts: 759
Joined: Mon Apr 26, 2010 10:15 am
Thanked: 85 times
Followed by:3 members

by clock60 » Tue Mar 15, 2011 12:50 pm
here got B
what is remaider if
(a-b)^2 is divided by 9

(1) a-b=3m+2
(3m+2)^2=9m^2+12m+4,
9m^2 divisible by 9, remaider when (12m+4) is diveded by 9 is not fixed.
say m=1 then 12+4=16=9*1+7 remaider 7
m=2, 24+4=28=3*9+1 remaider 1 so insuff

(2) a-b=9k+2
(9k+2)^2=81k^2+36k+4, remaider is 4 fixed here
Top
User avatar
Legendary Member
Posts: 582
Joined: Tue Mar 08, 2011 12:48 am
Thanked: 61 times
Followed by:6 members
GMAT Score:740

by force5 » Tue Mar 15, 2011 2:40 pm
correct answer it shld be B
Top
Post new topic Post Reply
• Page 1 of 1