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 equations ensures a solution.

Does p^2 = q if p is a prime number?

(1) q^2 - p^2 = 0

(2) p^2 = 49

according to variable approach method, since we have 2 variables (p,q) in the original condition we need 2 more to match the number of variables and equations. we have 1 each in 1) and 2), therefore C is likely the answer. Using both 1) & 2) together we have p=7, q=-7,7 and since no is the answer for p^2=49=7,-7, the condition is sufficient and the answer is C. but since the case if trivial, using common mistake type 4(A) we have 1) p^2=q^2 means q^2=q?, therefore q=0,1?. then we get p^2=0,1? and p=-1,0,1? and thus p is not a prime number, with answer as no. Therefore the condition is sufficient and the answer is A.

_________________

MathRevolution: Finish GMAT Quant Section with 10 minutes to spare

The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.

Find a 10% off coupon code for GMAT Club members.

“Receive 5 Math Questions & Solutions Daily”

Unlimited Access to over 120 free video lessons - try it yourself

See our Youtube demo