BTGModeratorVI wrote: ↑Thu Mar 19, 2020 5:31 am
If y < x < 0, which of the following CANNOT be true?
A. x·y > 2
B. x−y > 2
C. x/y > 2
D. x+y > −2
E. y/x < 2
Answer:
C
Source: Economist GMAT
We can let x = -1 and y = -4. So we have:
A. xy = (-1)(-4) = 4 > 2 ? → Yes
B. x - y = (-1) - (-4) = 3 > 2 ? → Yes
C. x/y = (-1)/(-4) = 1/4 > 2 ? → No
Since we are using actual numbers, let’s make sure the last two choices are also true before we can determine whether C is the correct answer.
D. x + y = (-1) + (-4) = -5 > -2 ? → No
E. y/x = (-4)/(-1) = 4 > 2 ? → Yes
Since both C and D give a “No” answer, we need to analyze them further. One way we can do that is to use another pair of numbers for x and y. So let’s let x = -0.5 and y = -1 and test them on choices C and D:
C. x/y = (-0.5)/(-1) = 0.5 > 2 ? → No
D. x + y = (-0.5) + (-1) = -1.5 > -2 ? → Yes
We can now see that the correct answer must be C.
Answer: C
