|
Author |
Message |
|
TAGS:
|
|
|
VP
Joined: 22 Nov 2007
Posts: 1108
Followers: 6
Kudos [?]:
80
[0], given: 0
|
If x is a positive integer, is the remainder 0 when 3x + 1 [#permalink]
 19 Jan 2008, 11:53
If x is a positive integer, is the remainder 0 when 3x + 1 is divided by 10?
(1) x = 4n + 2, where n is a positive integer.
(2) x > 4
|
|
|
|
|
|
|
Director
Joined: 12 Jul 2007
Posts: 875
Followers: 8
Kudos [?]:
135
[0], given: 0
|
Basically is X an integer with 3 in the units digit: 3, 13, 23, 33, etc
1. Multiples of 4 are: 4, 8, 12, 16, 20, 24, 28, 32 etc. None of these numbers + 2 will give us 3 in the units digit SUFFICIENT
2. x>4 doesn't help us because X could be 12 (not work) or 13 (works) INSUFFICIENT
taken together we learn nothing new either
Answer A
|
|
|
|
|
|
SVP
Joined: 28 Dec 2005
Posts: 1612
Followers: 1
Kudos [?]:
53
[0], given: 2
|
should be A.
You can see from A that 4n+2 always gives an even number, and plugging the result into 3x+1 always gives an odd number. All multiples of ten are even numbers, so you'll never have a perfect multiple of 10.
With B, you can have n=5 which doesnt give a remainder of 0, or n=13, which does. Insuff.
|
|
|
|
|
|
Senior Manager
Joined: 02 Aug 2007
Posts: 348
Location: Greater New York City area
Schools: Tuck, Ross (R1), Duke, Tepper, ISB (R2), Kenan Flagler (R2)
Followers: 3
Kudos [?]:
20
[0], given: 0
|
Should be A as explained by eschn3am
|
|
|
|
|
|
CEO
Joined: 29 Mar 2007
Posts: 2618
Followers: 13
Kudos [?]:
142
[0], given: 0
|
marcodonzelli wrote: If x is a positive integer, is the remainder 0 when 3x + 1 is divided by 10?
(1) x = 4n + 2, where n is a positive integer.
(2) x > 4 1: Suff. Notice that X must be even. b/c 4(n) is even and 2 is even and E+E= even. Also notice that only when x has a 3 in its units digit can 3x+1 be divisible by 10. Since E+E will never equal an odd. the remainder cannot be 0. 2: X can be 5 or 13.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Similar topics |
Author |
Replies |
Last post |
|
Similar
Topics:
|
 |
|
|
If x is a positive integer, is the remainder 0 when (3^x +
|
trickygmat |
5 |
28 Oct 2005, 08:04 |
|
|
|
|
If x is a positive integer, is the remainder 0 when (3x +
|
ricokevin |
2 |
17 Feb 2007, 03:29 |
|
|
|
|
If x is a positive integer, is the remainder 0 when 3^x + 1
|
Jcpenny |
2 |
11 Nov 2008, 13:59 |
|
|
|
|
If x is a positive integer, is the remainder 0 when 3^x + 1
|
gorden |
1 |
11 Nov 2008, 17:49 |
|
|
|
 |
If x is a positive integer, is the remainder 0 when (3x + 1)
|
curtis0063 |
2 |
02 Jan 2013, 09:00 |
|
|
|
|
|
|
close
