|
Author |
Message |
|
TAGS:
|
|
|
Intern
Joined: 08 Jul 2009
Posts: 6
Followers: 0
Kudos [?]:
0
[0], given: 0
|
I'm having some issues with questions about multiples, [#permalink]
 23 Jul 2009, 16:17
Question Stats:
0% (00:00) correct
 0% (00:00) wrong based on 0 sessions
I'm having some issues with questions about multiples, clearly.
Is the integer n a multiple of 15?
1) n is a multiple of 20
2) n + 6 is a multiple of 3
I'm not understanding how they got to the OA, which is C.
Thanks for your help!
|
|
|
|
|
|
|
Senior Manager
Joined: 04 Jun 2008
Posts: 308
Followers: 5
Kudos [?]:
73
[0], given: 15
|
Re: Is n a multiple of 15? [#permalink]
23 Jul 2009, 20:05
stmt1
n must be a multiple of 3 and also of 5 , but 20 is just 4 and 5, we dont know about 3.
stmt 2
n+6 is divisible by 3 - not sufficient
combine
consider all multiples of 20, such that n + 6 is divisible by 3.
20 + 6.....not divisible by 3
40 + 6.... no....40 not by 15
60 + 6..... yes, also 60 is divisible 15
another way: also, a multiple of 20 will be divisible by 5
further, if n+6 is divisible by 3, n is also divisible by 3, so it is also divisibly by 15.
|
|
|
|
|
|
Manager
Joined: 10 Jul 2009
Posts: 174
Followers: 1
Kudos [?]:
17
[0], given: 8
|
Re: Is n a multiple of 15? [#permalink]
23 Jul 2009, 20:40
For n to be a multiple of 15 it should be a multiple of both 3 & 5
from 1)
n is a multiple of 20 -> n is a multiple of both 5, 2^2
from 2)
n + 6 is a multiple of 3
that implies n is a multiple of 3
combining 1 and 2 we get to know n is multiple of 3,5, 2^2
So the answer is "C"
|
|
|
|
|
|
|
Re: Is n a multiple of 15?
[#permalink]
23 Jul 2009, 20:40
|
|
|
|
|
|
|
|
|
|
|
close
