BTGmoderatorDC wrote: ↑Sat Dec 21, 2019 8:12 pm
In quadrilateral ABCD, is angle BCD a right angle?
(1) Angle ABC is a right angle.
(2) Angle ADC is a right angle.
OA
E
Source: Official Guide
Target question: Is angle BCD a right angle?
When I SCAN the two statements, they both feel insufficient, AND I’m pretty sure I can identify some cases with conflicting answers to the
target question. So, I’m going to head straight to……
Statements 1 and 2 combined
Here are two quadrilaterals that satisfy BOTH statements:
CASE A: ABCD is a square
In this case, the answer to the target question is
YES, angle BCD is a right angle
CASE B: ABCD is not a square
In this case, the answer to the target question is
NO, angle BCD is not a right angle
Since we cannot answer the
target question with certainty, the combined statements are NOT SUFFICIENT
Answer: E
Cheers,
Brent
