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# is integer n a multiple of 15? 1) n is a multiple of 20 2) n

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VP
Joined: 30 Jun 2008
Posts: 1026
is integer n a multiple of 15? 1) n is a multiple of 20 2) n [#permalink]

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20 Sep 2008, 08:51
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is integer n a multiple of 15?

1) n is a multiple of 20
2) n + 6 is a multiple of 3
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"You have to find it. No one else can find it for you." - Bjorn Borg

Retired Moderator
Joined: 05 Jul 2006
Posts: 1747
Re: DS - Number Theory [#permalink]

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20 Sep 2008, 09:16
amitdgr wrote:
is integer n a multiple of 15?

1) n is a multiple of 20
2) n + 6 is a multiple of 3

IS n = 3*5 * X,

FROM 1

N = 2^2 * 5 *Y ( Y CAN BE ANYTHING - WE ARE NOT SURE IT INCULDES A 3 AS A FACTOR OR NOT?? ).........INSUFF

FROM 2

FOR N+6 TO BE A MULTIPLE OF 3 THUS N IS IN THE FORM = 3*Z ( Z IS NOT A MUST A MULTIPLE OF 5)..........INSUFF

N IS A MULTIPLE OF 3" FROM2" AND A MULTIPLE OF 5 "FROM1" THUS IT IS A MULTIPLE OF 15.

VP
Joined: 17 Jun 2008
Posts: 1373
Re: DS - Number Theory [#permalink]

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20 Sep 2008, 23:01
amitdgr wrote:
is integer n a multiple of 15?

1) n is a multiple of 20
2) n + 6 is a multiple of 3

1) n=20,40,60,80 etc INSUFFI
2)n can be 3,9,27 etc hence ISUFFI

1) and 2) n is a multple of 20 and divi by 3 hence div by 15 IMO C
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Intern
Joined: 13 Aug 2008
Posts: 17
Re: DS - Number Theory [#permalink]

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21 Sep 2008, 06:00
IMO C as well, but I think C tells us that n CANNOT be a multiple of 15. Consider multiples of 20 i.e. 20,40,60,80,100,120..where values of n satisfying stmt are 66,126,186,246..none of them are multiples of 15. Hence both stmts together are sufficient to tell us that n isNOT a multiple of 15
VP
Joined: 05 Jul 2008
Posts: 1401
Re: DS - Number Theory [#permalink]

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21 Sep 2008, 21:58
ankush83gupta wrote:
IMO C as well, but I think C tells us that n CANNOT be a multiple of 15. Consider multiples of 20 i.e. 20,40,60,80,100,120..where values of n satisfying stmt are 66,126,186,246..none of them are multiples of 15. Hence both stmts together are sufficient to tell us that n isNOT a multiple of 15

66,126,186 are values of n+6 and NOT n. C is still the correct answer though
Re: DS - Number Theory   [#permalink] 21 Sep 2008, 21:58
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