BTGModeratorVI wrote: ↑Wed Feb 03, 2021 10:30 am
In the xy-plane, line k passes through the point (1, 1) and line m passes through the point (1, -1). Are the lines k and m perpendicular to each other ?
(1) Lines k and m intersect at the point (1, -1)
(2) Line k intersects the x-axis at the point (1, 0)
Answer:
E
Source: official guide
Target question:
Are lines K and m perpendicular to each other?
IMPORTANT: Since line K passes through the point (1, 1), statements 1 and 2 both have the same effect of "locking" line K into exactly one position. In fact, statements 1 and 2 essentially provide the exact same information. As such, it's either the case that each statement is sufficient (D) or each statement is not sufficient (E).
Since neither statement locks line M into any certain position, line M is free to be in lots of different positions, as long as it passes through the point (1, -1)
Okay, let's jump right to . . .
Statements 1 and 2 combined:
Here are two possible scenarios that satisfy statements 1 and 2.
Scenario a:
In this instance,
lines M and K are perpendicular.
Scenario b:
In this instance,
lines M and K are not perpendicular.
Since we cannot answer the
target question with certainty, the combined statements are NOT SUFFICIENT
Answer = E
Aside: This concept of "locking in" shapes on Geometry DS questions is discussed in much greater detail in this video:
https://www.gmatprepnow.com/module/gmat- ... cy?id=1103
Cheers,
Brent
