Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized for You

we will pick new questions that match your level based on your Timer History

Track Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

If x is an integer and y = 3x + 2, which of the following [#permalink]
01 Oct 2007, 01:45

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'm struggling to find the best approach to do this in 2 minutes. I started plugging in numbers but there should be a better approach. Please help. Thanks

Re: Number Properties - Approach help!! [#permalink]
01 Oct 2007, 02:03

alimad wrote:

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'm struggling to find the best approach to do this in 2 minutes. I started plugging in numbers but there should be a better approach. Please help. Thanks

Answer C; plugged in values of x but after a little thought which cut down the time to solve. Basically, I looked for multiples of the answer choices and if after subtracting two from these multiples, they were divisible by 3, I eliminated them.

Eg: To check for choice D, 7, I thought of a multiple of 7, that is 56; subtracted 2 to get 54; Since 54 is a multiple of 3, we can eliminate D.

Plug in x = 2 to eliminate A & E
Plug in x = 11 to eliminate B
Plug in x = 18 to eliminate D

Re: Number Properties - Approach help!! [#permalink]
13 Oct 2007, 14:52

X is an integer... This is important.

As such, you can re-write to

(y-2)/3 must not yield any remainder.

The set that works for this is {5, 8, 11, 14, 17, 20, 23, 26, 29, 32}
A eliminated by 32
B eliminated by 5
C not eliminated (note none of the numbers are divisible by 3...)
D eliminated by 14
E eliminated by 8

Re: Number Properties - Approach help!! [#permalink]
13 Oct 2007, 23:21

alimad wrote:

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'm struggling to find the best approach to do this in 2 minutes. I started plugging in numbers but there should be a better approach. Please help. Thanks

C,

(3x+2)/? is NEVER intenger.

(3x/?) + (2/?) is NEVER intenger

A) (3x/2) + (2/2)----------> out, cuz x can be 2
B) (3x/5) + (2/5)----------> not sure leave for now, move to the next
C) (3x/3*2) + (2/3*2)= x/2+1/3 for this to be an intenger x/2 must be +2/3 or -1/3, which is impossible given that x is an intenger.

gmatclubot

Re: Number Properties - Approach help!!
[#permalink]
13 Oct 2007, 23:21