firang wrote:

anyone get this one? I know i'm missing something very silly here, it's just not clicking, please help me out.

If k is an integer, and (35^2-1)/k is an integer, then k could be each of the following, EXCEPT

(A) 8

(B) 9

(C) 12

(D) 16

(E) 17

Let me try to explain how I would approach a problem like this. First take a quick look about the answer. What do you notice?

you have a prime number that is 17 and the other are multiples of 4 or 3.

Then I did 35*35 - 1 = 1224

First, I find out if the number is divisible by 17. Because if not you have your answer here.

1224/ 17 = 72

cross out option e

now you have to check with of the answer is multiple of 72, that is easy

A and B are multiple

C too

so the answer must be D

Other option you can know that 1224 is multiple of 9 because the digits of the numbers is multiple of 9 and of course is multiple of 2. To be multiple of 4 the last digit must be multiple of 4 in this case 24 is multiple of 4. For eight the last 3 digits. (224/8 = 28)

for me the first way was really fast, but of course other approaches must be there

so I am open to suggestions!!

I hope it helps