This is what I have: Is the integer z divisible by 6? 1) The

Question

This is what I have:

Is the integer z divisible by 6?

1) The greatest common factor of z and 12 is 3.
2) The greatest common factor of z and 15 is 15.

The book said the answer was  A  but what I got was  E . I am very confused.

Another question.

Is N divisible by 7?

1) N = x - y, where x and y are integers.
2) x is divisible by 7, and y is not divisible by 7.

Again, the book says the answer is  C  but what I got was  E .

Spidy001 · Answer

1. Sufficient

common factor of z and 12 is 3.

=> there is no 2 in Z . if there is 2 in z , then common factor would have been 6.
 => z has a 3 , but no 2.

for a number to be divisible by 6. its needs to have both 2 and 3.
 => z is not divisible by 6. Enough to answer the question.
 Hence Sufficient.

2. Not sufficient
 
 common factor of z and 15 is 15.

=> z has 3 in it.

but we don't know about 2. if z has a 2 , then it will be divisible by 6. if not it wont be divisible by 6.
 Not sufficient.

Answer is A.

Silver89 · Answer

@Lstadt 
i think you solved it in the right way but you have problem in understanding DS
for (is) questions : if the answer is yes OR no, it is Sufficient
if the answer maybe it's NOT sufficient

Lstadt · Answer

Oh. I see what you mean. This clarifies it. However, how about the other question that I posted?

Is N divisible by 7?

1) N = x - y, where x and y are integers.
2) x is divisible by 7, and y is not divisible by 7.

The book (MGMT) is saying the answer is C. Does that mean that both statements are sufficient to prove that N is NOT divisible by 7, hence the combining them together will give us a NO answer?

Silver89 · Answer

first statement is not sufficient because it is not giving any specific information about N
the second one also not sufficient because it's not telling us anything about N
by combining the two we can find that N= multiple of 7 - not multiple of 7
so it is impossible to be a multiple of 7 and the answer is c
good luck man on you prep

Silver89 · Answer

yes man you are on the right way ............ yes or no is sufficient maybe in not sufficient i'm studying with MGMAT too :-D

Lstadt · Answer

Thanks Silver, I am studying with MGMAT too. I can barely put enough time to finish things but I am really liking their presentation and examples. I have not taken the prep test yet. I need to get a high score. Good luck to you my friend

This is what I have: Is the integer z divisible by 6? 1) The

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