If anyone wishes to attempt the original question, here's one solution:
Target question: What is the measure of angle BAD?
Statement 1: AD bisects angle BAC
Since we don't know the measure of angle BAC, there's no way to determine
the measure of angle BAD
Since we cannot answer the
target question with certainty, statement 1 is NOT SUFFICIENT
Statement 2: BAC is an isosceles right triangle
This statement contains no information about D, so there's no way to determine
the measure of angle BAD
Since we cannot answer the
target question with certainty, statement 2 is NOT SUFFICIENT
Statements 1 and 2 combined
If BAC is an isosceles right triangle, then angle BAC = 45 degrees
If AD bisects angle BAC, then
angle BAD = 22.5 degrees
Since we can answer the
target question with certainty, the combined statements are SUFFICIENT
Answer =
C
Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
