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Number Properties [#permalink] New post 10 Sep 2006, 12:43
This is from the OG quant review problem solving section. I'm not satisfied with the book's explanation... I would appreciate a more detailed explanation. Thanks.


125. If x is an integer and y=3x+2, which of the following CANNOT be a divisor of y?

A. 4
B. 5
C. 6
D. 7
E. 8



I narrowed it down to C or D but don't know how to arrive at the OA. Please explain. Thanks.
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Re: Number Properties [#permalink] New post 10 Sep 2006, 12:55
govinam wrote:
This is from the OG quant review problem solving section. I'm not satisfied with the book's explanation... I would appreciate a more detailed explanation. Thanks.


125. If x is an integer and y=3x+2, which of the following CANNOT be a divisor of y?

A. 4
B. 5
C. 6
D. 7
E. 8



I narrowed it down to C or D but don't know how to arrive at the OA. Please explain. Thanks.


Try plugging numbers, trying for x=0,1,2,3,4,5 we get
y = 2,5,8,11,14,17

Hence we can easily see that 4,5, & 8 are out. Additionally 14 is divisible by 7. Hence answer is C.
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 [#permalink] New post 10 Sep 2006, 15:34
I believe the answer is c = 6

6 has two factors 3,2


y=3x+2 can never be devisible by three

f(0) = 2
f(1) = 5
f(2) =8
f(3) = 11

ie y belongs to { 2,5,8,11,.....} it starts with 2 and a jump of 3 between any two values in the set

thus y can never take a value that is divisible by 3
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 [#permalink] New post 10 Sep 2006, 22:02
yezz wrote:
I believe the answer is c = 6

6 has two factors 3,2


y=3x+2 can never be devisible by three

f(0) = 2
f(1) = 5
f(2) =8
f(3) = 11

ie y belongs to { 2,5,8,11,.....} it starts with 2 and a jump of 3 between any two values in the set

thus y can never take a value that is divisible by 3

This is the best way.
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  [#permalink] 10 Sep 2006, 22:02
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