Is z an integer? (1) z/3 is an integer. (2) z/2 is NOT an integer.

Question

Is z an integer?

(1) z/3 is an integer.

(2) z/2 is NOT an integer.

chetan2u · Answer

(1) z/3 is an integer.
Let  \frac{z}{3}=k =integer...z=3k=3*integer=integer
ans is YES.
Suff

(2) z/2 is NOT an integer
If z= \frac{3}{2} , answer is NO
If z= 3, answer is YES
Insuff

A

desziky · Answer

Hi, I got this question wrong because I assumed that Z as "2".

Is 2 an integer? Yes/No.
1. 2/3 is an integer. NO
2. 2/2 is not an integer. NO - it is an integer.

Can anyone explain how does this IF question work? I am sometimes confused with this yes/no question..

MathRevolution · Answer

Forget conventional ways of solving math questions. For DS problems, the VA (Variable Approach) method is the quickest and easiest way to find the answer without actually solving the problem. Remember that equal numbers of variables and independent equations ensure a solution. Visit https://www.mathrevolution.com/gmat/lesson for details. The first step of the VA (Variable Approach) method is to modify the original condition and the question. We then recheck the question. We should simplify conditions if necessary. Since we have 1 variable (z) and 0 equations, D is most likely to be the answer. So, we should consider each condition on its own first. Condition 1) We have z = 3k for some integer k. Then z is an integer. Thus, the answer is 'yes'. Since condition 1) yields a unique solution, it is sufficient Condition 2) If z = 1, then z/2 is not a integer, z is an integer and the answer is 'yes'. If z = 1/2, then z/2 is not a integer, z is not an integer and the answer is 'no'. Since condition 2) does not yield a unique solution, it is not sufficient Therefore, A is the answer. If the original condition includes “1 variable”, or “2 variables and 1 equation”, or “3 variables and 2 equations” etc., one more equation is required to answer the question. If each of conditions 1) and 2) provide an additional equation, there is a 59% chance that D is the answer, a 38% chance that A or B is the answer, and a 3% chance that the answer is C or E. Thus, answer D (conditions 1) and 2), when applied separately, are sufficient to answer the question) is most likely, but there may be cases where the answer is A,B,C or E.

reynaldreni · Answer

Statement-1
z/3=int k
z = 3*k 
product of two ints must be a int.
Sufficient

Statement-2
z/2=decimal d
z = 2*d
z may or may not be an int
d=1.5, 1.5*2 = 3 (int)
d=1.2, 1.2*2 = 2.4(deci)
Insufficient

OA <- A

Is z an integer? (1) z/3 is an integer. (2) z/2 is NOT an integer.

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GMAT Data Sufficiency (DS) Questions

Is z an integer? (1) z/3 is an integer. (2) z/2 is NOT an integer.

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