giuliab3 wrote:

HanoiGMATtutor wrote:

giuliab3 wrote:

If AD is 6, and ADC is a right angle, what is the area of triangular region ABC?

(1) Angle ABD = 60°

(2) AC = 12

After getting this question wrong (above), I realized I still do not distinguish what conditions are SUFFICIENT for assuming that a triangle is a 30-60-90 triangle and what conditions show that the triangle COULD be a 30-60-90 but I cannot assume it based on the information given.

So what conditions are sufficient for me to assume a triangle is indeed a specific type of triangle?

Thank you!

Does the question specify where B is located with respect to ADC?

It´s the problem discussed in this link:

https://gmatclub.com/forum/if-ad-is-6-a ... 01200.htmlGot it. A triangle is defined when you know two angles and the side in between, two sides and the angle in between, or all 3 sides. Obviously, when you know two angles, you also know the third one, and in a right triangle, once you know two sides, you also know the third one. See you if these hints help you make sense of the problem.

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