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Gmat prep - remainder

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Source: — Data Sufficiency |
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Re: Gmat prep - remainder

by Vemuri » Tue May 05, 2009 7:48 pm
IMO B

Stmt1: 21x+r=n. The reminder is odd. That means the reminder can be 1,3 & 5. This info is not sufficient.

Stmt2: 28x+r=n. The reminder is 3. If n=59, then the reminder is 3 when divided by 28 & 7. The same is the case with all multiples of 28. This statement is sufficient.
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by Uri » Wed May 06, 2009 12:45 pm
IMO (B)

observe that both 21 and 28 are multiples of 7. thus whatever is the reminder after division by 21 or 28, will also lead to the reminder after division by 7. if the reminder is less than 7 after division by 21 or 28, then this will also be the reminder after division by 7 if reminder is greater than 7 after division by 21 or 28, then the reminder after division by 7 will equal the reminder after the following calculation:
(reminder after division by 21 or 28)/7
eg. 38/21 gives the reminder 17. so 38 when divided by 7 will give reminder= reminder when 17 is divided by 7
=3

(1) is not sufficient. r can be 1,3 or 5.
(2) ensures that the reminder is 3. hence sufficient.
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by abhinav85 » Wed May 06, 2009 1:56 pm
I can't see ques which are given in this format .docx???

what is that?
and how to open these kind of files????
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by maihuna » Sat May 09, 2009 1:45 am
Stmt 1 : n = 21k + r
where r could be: 1 3 5 7 9 11 13 15 17 19
remainder with 7: 1 3 5 0 2 4 6 1 3 5

So remainder could be : 0 1 2 3 4 5 and so not sufficient

Stmt 2: n = 28k + 3 so remainder with 3 will be 3 sufficient
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