Might sound silly..but i have a doubt

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ashhchdg: Junior | Next Rank: 30 Posts; Posts: 14; Joined: Sun Aug 14, 2011 4:25 am; Thanked: 1 times

by ashhchdg » Sun Aug 28, 2011 9:13 am

Sorry typo error...i have corrected the question.

If x and y are integers between 10 and 99, inclusive, is (x-y)/9 an integer?
(1) x and y have the same two digits, but in reverse order.
(2) The tens' digit of x is 2 more than the units digit, and the tens digit of y is 2 less than the units digit.

OA is A
I checked the beat the gmat forums for the answer explanation and found them correct. But my problem lies in here.What if both x and y are the same ?...will not the first option be ruled out in that case ?

Last edited by ashhchdg on Sun Aug 28, 2011 5:21 pm, edited 1 time in total.

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Source: Beat The GMAT — Data Sufficiency | Sun Aug 28, 2011 9:13 am

force5: Legendary Member; Posts: 582; Joined: Tue Mar 08, 2011 12:48 amFollowed by: 6 members; Thanked: 61 times; GMAT Score:740

by force5 » Sun Aug 28, 2011 10:15 am

please check the question again... the question is not complete...

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prateek_guy2004: Master | Next Rank: 500 Posts; Posts: 398; Joined: Tue Jul 26, 2011 11:39 pmFollowed by: 6 members; Location: India; Thanked: 41 times

by prateek_guy2004 » Sun Aug 28, 2011 2:18 pm

I dont think it should be A, or the ques...is left out with some more words....

Don't look for the incorrect things that you have done rather look for remedies....

https://www.beatthegmat.com/motivation-t90253.html

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navami: Legendary Member; Posts: 540; Joined: Sat Dec 20, 2008 7:24 pmFollowed by: 6 members; Thanked: 37 times

by navami » Wed Aug 31, 2011 1:04 am

Ans should be a.

If we consider option 1.
assume x = 21 y y = 12 x-y = 9

Hence x-y/9 = integer
Now consider x = 31 y = 13
x - y = 18

now consider x = 71 y = 17

x-y = 54

This time no looking back!!!
Navami

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knight247: Legendary Member; Posts: 504; Joined: Tue Apr 19, 2011 1:40 pmFollowed by: 11 members; Thanked: 114 times

by knight247 » Wed Aug 31, 2011 1:25 am

ashhchdg wrote:Sorry typo error...i have corrected the question.

If x and y are integers between 10 and 99, inclusive, is (x-y)/9 an integer?
(1) x and y have the same two digits, but in reverse order.
(2) The tens' digit of x is 2 more than the units digit, and the tens digit of y is 2 less than the units digit.

OA is A
I checked the beat the gmat forums for the answer explanation and found them correct. But my problem lies in here.What if both x and y are the same ?...will not the first option be ruled out in that case ?

x and y can't be the same. From only the question stem, we have no info about x and y. But from statement 1 we get that x and y are two distinct numbers with digits reversed. So when the statement specifically tells us that x and y are different, how can we assume that they are the same? That being said

Statement(1) Lets try different combinations 72-27=45 which is divisible by 9
91-19=72 which is divisible by 9
56-65=9. Whichever combination you try, the answer will be divisible by 9. Hence, SUFFICIENT

Statement(2)
let x be 86 and y be 46 so 86-46=40 not divisible by 9
let x be 64 and y be 46 so 64-46=18 which is divisible by 9. We get conflicting answers hence INSUFFICIENT

Answer is A. Hope your doubt has been clarified.

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SticklorForDetails: GMAT Instructor; Posts: 66; Joined: Wed Jul 20, 2011 3:39 pmFollowed by: 22 members; Location: New York, NY; Thanked: 39 times; GMAT Score:780

by SticklorForDetails » Wed Aug 31, 2011 9:38 pm

ashhchdg wrote:Sorry typo error...i have corrected the question.

If x and y are integers between 10 and 99, inclusive, is (x-y)/9 an integer?
(1) x and y have the same two digits, but in reverse order.
(2) The tens' digit of x is 2 more than the units digit, and the tens digit of y is 2 less than the units digit.

OA is A
I checked the beat the gmat forums for the answer explanation and found them correct. But my problem lies in here.What if both x and y are the same ?...will not the first option be ruled out in that case ?

If x and y are the same, for example, x = 33 and y = 33 (in reverse order, the same two digits), then (x-y)/9 = (33-33)/9 = 0/9 = 0. 0 is an Integer. Still Yes, still Sufficient.

However, I agree that there is nothing that implies that the digits must be distinct or that x and y must be distinct. You are absolutely right to consider the possibility ... but it results in the same answer!

Experienced tutors, customized study plans, personalized service.

www.GothamTutors.com/adam.html

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prateek_guy2004: Master | Next Rank: 500 Posts; Posts: 398; Joined: Tue Jul 26, 2011 11:39 pmFollowed by: 6 members; Location: India; Thanked: 41 times

by prateek_guy2004 » Thu Sep 01, 2011 2:38 am

knight247 wrote:
ashhchdg wrote:Sorry typo error...i have corrected the question.

If x and y are integers between 10 and 99, inclusive, is (x-y)/9 an integer?
(1) x and y have the same two digits, but in reverse order.
(2) The tens' digit of x is 2 more than the units digit, and the tens digit of y is 2 less than the units digit.

OA is A
I checked the beat the gmat forums for the answer explanation and found them correct. But my problem lies in here.What if both x and y are the same ?...will not the first option be ruled out in that case ?
x and y can't be the same. From only the question stem, we have no info about x and y. But from statement 1 we get that x and y are two distinct numbers with digits reversed. So when the statement specifically tells us that x and y are different, how can we assume that they are the same? That being said

Statement(1) Lets try different combinations 72-27=45 which is divisible by 9
91-19=72 which is divisible by 9
56-65=9. Whichever combination you try, the answer will be divisible by 9. Hence, SUFFICIENT

Statement(2)
let x be 86 and y be 46 so 86-46=40 not divisible by 9
let x be 64 and y be 46 so 64-46=18 which is divisible by 9. We get conflicting answers hence INSUFFICIENT

Answer is A. Hope your doubt has been clarified.

Great approach mate!!

Don't look for the incorrect things that you have done rather look for remedies....

https://www.beatthegmat.com/motivation-t90253.html

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