Hi All,
This DS question requires a little bit of Geometry "math" and the knowledge of a couple of very specific Geometry terms.
We're told that points A and B lie on a Circle. We're asked if the AREA of the circle is GREATER than 80pi. This is a YES/NO question.
Fact 1: The length of MINOR ARC AB is 6pi.
By definition, a 'minor arc' is LESS than 180 degrees of the circle.
IF....
the minor arc 6pi was 179.9999 degrees of the circle...
then the circumference of the circle would be almost 12pi
and the radius would be almost 6
the area would be almost 36pi and the answer to the question is NO.
IF....
the minor arc 6pi was 30 degrees of the circle...
then the circumference of the circle would be 72pi
and the radius would be 36
the area would be almost (36^2)pi and the answer to the question is YES.
Fact 1 is INSUFFICIENT
Fact 2: The length of chord AB is 18.
By definition, a "chord" is a straight line that connects any two points on the circumference of a circle. The LARGEST chord is the diameter.
IF....
the chord 18 IS the diameter....
then the radius is 9
the area is 81pi and the answer to the question is YES
IF....
the chord 18 is NOT the diameter....
then the diameter is GREATER than 18
and then the radius is GREATER than 9
the area is GREATER than 81pi and the answer to the question is STILL YES
With the information in Fact 2, the answer to the question is ALWAYS YES.
Fact 2 is SUFFICIENT
Final Answer:
GMAT assassins aren't born, they're made,
Rich