Question 222 Problem Solving 2018 GMAT Official Guide

Question 222 Problem Solving 2018 GMAT Official Guide

Video explanation: If 1/x – 1/x+1 = 1/x+4, then x could be

Comments

Alexsays

As you probably already know, you can’t divide by zero; so, that automatically rules out 0, -1, and -4 from the answer choices. Thus, leaving you with -2 and -3. If you do a calculation involving the two negative integers, it could save time in the exam.

Yes, that works really well in this case. By eliminating three answer choices, and plugging in the remaining two makes it very reasonable to isolate the answer in this case. But this could become a pain if they had changed the answer choices to $-5$, $-3$, $-2$, $2$, and $1$. I always recommend my students to be flexible in approaching GMAT problems, one never knows what the most efficient method for a particular problem is.

Alex says

As you probably already know, you can’t divide by zero; so, that automatically rules out 0, -1, and -4 from the answer choices. Thus, leaving you with -2 and -3. If you do a calculation involving the two negative integers, it could save time in the exam.

GMAT Quantum says

Hi Alex,

Yes, that works really well in this case. By eliminating three answer choices, and plugging in the remaining two makes it very reasonable to isolate the answer in this case. But this could become a pain if they had changed the answer choices to $-5$, $-3$, $-2$, $2$, and $1$. I always recommend my students to be flexible in approaching GMAT problems, one never knows what the most efficient method for a particular problem is.

Thanks for the comment.

Dabral