divisor

AIM TO CRACK GMAT wrote:If x=8y+11 then which of the following cannot be a divisor of x.(y is a whole number)?

a) 3
b) 5
c) 7
d) 12

[spoiler]OA = D[/spoiler]

x = 8y + 11
So, x = (EVEN NUMBER)(y) + ODD
If y is an integer, then (EVEN NUMBER)(y) = EVEN,
So x = EVEN + ODD
Finally, x = ODD

If x is odd, it cannot be divisible by an even number.
So, x cannot be divisible by 12 (since 12 is even)

Answer: D

Cheers,
Brent

Hi AIM,

This question does not follow typical GMAT "design", so you should be suspicious of its representativeness.

While Brent presented the Number Property behind this question, you can easily solve it with "brute force" math. Here's how:

We're told that Y is an integer.
If Y = 1, then X = 8 + 11 = 19 Can't eliminate any answers
If Y = 2, then X = 16 + 11 = 27, Eliminate A
If Y = 3, then X = 24 + 11 = 35, Eliminate B and C

Final Answer: D

GMAT assassins aren't born, they're made,
Rich