-
vijaynarayanan
- Senior | Next Rank: 100 Posts
- Posts: 40
- Joined: Sat Jan 30, 2010 10:38 am
Vijay,
Just to know what is the source of this question?
BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course
Redeem
Featured Course
Target Test Prep GMAT OnDemand
Scott Woodbury-Stewart’s private virtual classroom — 400 hours of master-class video lessons for the GMAT Focus Edition.
- 715+ score guarantee — highest in the industry (99th percentile)
- 52 chapters · 1,500+ lessons · 4,000+ practice questions
- 400 hours of video · 1,500+ instructor-led HD smartboard lessons
- 300,000+ students accepted to Harvard, Stanford, Wharton, Booth & Sloan & more
- 24/7 live support + weekly Zoom office hours with GMAT instructors
- TTP AI Assist — 24/7 AI-powered virtual tutor for instant help
- 1,200+ flashcards + AI-powered study assistant & daily calendar
- OnDemand, LiveTeach & GMAT Bootcamp formats available
- Also: GRE, SAT Math & Executive Assessment courses
- MBA Admissions Consulting now available
- 🏆 2025 EdTech Breakthrough Award: Test Prep Solution Provider of the Year
- 200,000+ students served
- 5-day free trial — $0 to start, no auto-billing, cancel anytime
★★★★★
5.0
(559 reviews)
130-pt guarantee
$0 to start
then $127/mo
Numbers
Source: Beat The GMAT — Data Sufficiency |
x-y = 9k ???vijaynarayanan wrote:
Kindly help me solve.
Correct Answer: A
let x= 10a +b
y = 10b+a
x-y = 9(a-b)
a and b are integers. So x-y is a multiple of 9.
SUFF
x = 10a1+b1
y = 10a2+b2
a1 = b1+2
a2 = b2-2
x-y = 11b1+20 - 11b2-20
=11(b1-b2)+40
=40+11 or 40 +22 or 40+33 or 40+44 or.....
Cannot be multiple of 9
pick A
Yeah you are right.. But, x and y are integers between 10 and 99.selango wrote:Praveen buddy.....
40+77=117 is divisible by 9.
So maximum difference among them is 99-10 =89
So x-y cannot be 117.
for x-y we will get 51, 62, 73, 84 only. Forgot to mention this in above post
None of these are divisible by 9.
Hope this helps!!
all is said about this problem, my answer also A and my two cents
is (x-y)/9=integer
(1) x=10a+b, y=10b+a. so
x-y=10a+b-10b-a=9a-9b=9(a-b)-must be divisible by 9
so sufficient
(2) x=10a+(a-2)=11a-2
y=10b+(b+2)=11b+2
x-y=11a-2-11b-2=11(a-b)-4, now let us check
if a-b=1, 11-4=7 not divisible by 9
a-b=2, 11*2-4=18 divisible by 9
a-b=3 11*3-4=29 not divisible by 9
as we have yes and no answers st2 insufficient
so A
is (x-y)/9=integer
(1) x=10a+b, y=10b+a. so
x-y=10a+b-10b-a=9a-9b=9(a-b)-must be divisible by 9
so sufficient
(2) x=10a+(a-2)=11a-2
y=10b+(b+2)=11b+2
x-y=11a-2-11b-2=11(a-b)-4, now let us check
if a-b=1, 11-4=7 not divisible by 9
a-b=2, 11*2-4=18 divisible by 9
a-b=3 11*3-4=29 not divisible by 9
as we have yes and no answers st2 insufficient
so A
i beg to differ...it says that x and y are integers between 10 and 99, not that their difference is between 10 and 99. so 40+77 is a valid argument in my opinion.kvcpk wrote:Yeah you are right.. But, x and y are integers between 10 and 99.selango wrote:Praveen buddy.....
40+77=117 is divisible by 9.
So maximum difference among them is 99-10 =89
So x-y cannot be 117.
for x-y we will get 51, 62, 73, 84 only. Forgot to mention this in above post
None of these are divisible by 9.
Hope this helps!!
Preet
Hi Preet,singhpreet1 wrote: i beg to differ...it says that x and y are integers between 10 and 99, not that their difference is between 10 and 99. so 40+77 is a valid argument in my opinion.
Preet
if x an y are integers between 10 and 99, themaximum difference x-y can be when
x is maximum and y is minimum
Maximum x possible is99, minimum y possible is 10
difrence is 99-10 = 89.
SO maximumvalue ofx-y is 89.
Hope this helps!!
that is true...i need to convince myself to do the maximum- minimum concept to get this straight.kvcpk wrote:Hi Preet,singhpreet1 wrote: i beg to differ...it says that x and y are integers between 10 and 99, not that their difference is between 10 and 99. so 40+77 is a valid argument in my opinion.
Preet
if x an y are integers between 10 and 99, themaximum difference x-y can be when
x is maximum and y is minimum
Maximum x possible is99, minimum y possible is 10
difrence is 99-10 = 89.
SO maximumvalue ofx-y is 89.
Hope this helps!!
thanks.
Preet
