If x is positive, is x prime?

Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.

If x is positive, is x prime?
(1) x^3 has exactly four distinct factors
(2) x^2−x−6=0


In the original condition, there is 1 variable(x), which should match with the number of equations. So you need 1 equation. For 1) 1 equation, for 2) 1 equation, which is likely to make the answer D.
For 1), the number of factors is 3+1=4 and x must be prime, which is yes and sufficient.
For 1), from (x-3)(x+2)=0, x=3 is only possible, which is yes and sufficient.
Thus, D is the answer.


 For cases where we need 1 more equation, such as original conditions with “1 variable”, or “2 variables and 1 equation”, or “3 variables and 2 equations”, we have 1 equation each in both 1) and 2). Therefore, there is 59 % chance that D is the answer, while A or B has 38% chance and C or E has 3% chance. Since D is most likely to be the answer using 1) and 2) separately according to DS definition. Obviously there may be cases where the answer is A, B, C or E.