Geometry Mgmat CAT Help

[transfer9858]

Hey everyone- I am having trouble understanding the answer to this question. Any help would be great, thanks.

For the triangle shown above, where A, B and C are all points on a circle, and line segment AB has length 18, what is the area of triangle ABC?

(1) Angle ABC measures 30°.

(2) The circumference of the circle is 18.


There is a picture and it looks like 18 is the hypotenuse. Since 18 is the hypotenuse, any triangle inscribed with a side of the diameter has to be a right angle. Then, since its 30 degrees, we can find the other 2 sides, so A would be sufficient, but it's C. My question is, is it C because even though on the picture it clearly looks like 18 is the diameter, we can't ASSUME it is, thus we need statement B to prove it? Thanks everyone

[rijul007]

Hey everyone- I am having trouble understanding the answer to this question. Any help would be great, thanks.

For the triangle shown above, where A, B and C are all points on a circle, and line segment AB has length 18, what is the area of triangle ABC?

(1) Angle ABC measures 30°.

(2) The circumference of the circle is 18.

Are you sure the data in this ques is correct??

Acc to the ques stem,
AB = 18 [Points A and B lie on the circumference of the circle]

Acc to statement 2,
Circumference = 18

Now, Even if the line segment AB was th largest chord [i.e. diameter]
Circumference would have been = pi*d = pi* 18 [which is greater than the diameter]

Please check the ques..

[rijul007]

For the triangle shown above, where A, B and C are all points on a circle, and line segment AB has length 18, what is the area of triangle ABC?

(1) Angle ABC measures 30°.

(2) The circumference of the circle is 18*PI.

Statement 1
Angle ABC measures 30°.

there are lots of different triangles possible..



INSUFFICIENT

Statement 2

This means that AB is a diameter
and angle subtended by the diameter on the circumference is 90 degrees
But again, lots of different orientations of right triangle fit here


INSUFFICIENT


Combining Statement 1 & 2
Only one type of triangle is possible
Angles 30-60-90 and hypotenus- 18
Area can be calculated


Option C

[transfer9858]

Hi Ya the question is correct- from manhattan gmat cat.