If a car moving at the speed of x km/hr travels a distance

x cannot be equal to zero because the car is moving and so has to have some speed. Equating to y is the natural way to solve this problem because you can then find what is impossible.

Plugging in values will be cumbersome for this problem because each choice is true only when y and x are related in a particular way. For example in choice 3 which is x-y / 2, if you chose x=60 and y =40, x-y / 2 =10 you might think that since the distance traveled comes out as different i.e., as 40 and 10, the choice is wrong. But it is actually true when x=3y. Finding the right values is very difficult.

So generally when it is the case that you may have to plug in many values to find whether a choice is correct or not, trying to plug in values and solve is not the right approach.

I have a very basic question. Why we are not considering quantity we are dealing with ?
How can we subtract distance with speed or vice-verse ?
Only possible functions should be y/x or x/y.Correct me if I am missing something.

Hi All,

This question can be solved by TESTing VALUES, but there's a particular pattern that you have to recognize to make the work "easy."

We're not really limited by anything in this question, so X and Y can be anything. Under normal circumstances, I won't TEST the number 1 in PS questions (as it often leads to duplicate answers), but here it's a great option (since we're looking to eliminate 4 answers, multiple TESTs are going to be likely anyway).

We're given information on speed (X km/hour) and distance (Y km). We're asked which of the 5 answer choices CANNOT be the distance traveled.

IF....
X = 2 and Y = 1
Answers A (2-1 = 1) and B (2/2 = 1) are POSSIBLE. Eliminate A and B.

IF....
X = 3 and Y = 1
Answer C ([3-1]/2 = 1) is POSSIBLE. Eliminate C.

IF....
X = 1 and Y = 1
Answer D (1/1 = 1) is POSSIBLE. Eliminate D.

Final Answer:

GMAT assassins aren't born, they're made,
Rich

The question seems to be a tricky one. And it needs a different approach. It is very difficult to identify the correct approach in the first go.

Speed of the car = x km/hr
Distance = y km

Lets start equating each options.
A. x-y = y -> x = 2y

B. x/2 = y -> x = 2y

C. (x-y)/2 = y -> x = 3y

D. y/x = y -> x =1

E. y-x = y -> x = 0

Since car is moving, so only option E seems impossible.

Answer E

The distance traveled is y km. We think the question asks for the expression that cannot be another way to express the distance traveled. Let’s analyze each answer choice.

A) x - y = y → x = 2y → This is fine as long as x is twice of y.

B) x/2 = y → x = 2y → This is fine since it’s same as choice A.

C) (x - y)/2 = y → x - y = 2y → x = 3y → This is fine as long as x is three times of y.

D) y/x = y → x = 1 → This is fine as long as x is 1.

E) y - x = y → x = 0 → This is not fine since the speed can’t 0 km/hr.

Answer: E

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.