minwoswoh wrote:
I think you don´t need to do any calculation or even draw a diagram for this problem. Just use your common sense.
- Remember that the sum of the interior angles of any quadrilateral is 360º.
- The question asks for the value of a specific angle of the four (angle ADC)
- You can´t assume that other angle/s has/have the same value as ADC has since you don´t know whether this quadrilateral is a square, rectangle, rhombus, or any other type of quadrilateral.
(1) Statement 1 says: All the other 3 angles = 280. Therefore, ADC must equal 80. Sufficient.
(2) Statement 2 has a similar format but says: 2 of the angles + ADC = 300. You can´t know what ADC is since ABC is now not included in this equation. Insufficient.
Takeaways from this question
- Know your Geometry formulae cold
- Don´t assume things away (especially in DS Geometry)
- Be aware of DS Combo Questions
- Be aware of similar-format statements. One could be sufficient and the other insufficient!
Thank you for the takeaway.
Action item for me: dont get intimidated by geometry questions, especially because I am so used to solving the types of geometry questions where a figure or a shape is given.
Room for improvement: I spent too much time trying to figure-out things that are not helpful at all, given the question asked.
Eg I stalled because I dont know how to draw this quadrilateral. In fact, dare I say that "forcing" this problem to be graphed on my paper is not only not helpful; it makes the problem more complex because my brain is distracted on the wrong thing, such as " I wonder if this figure is a square or a rhombus ? ".
In the forthcoming exam, I need to be more comfortable with solving abstraction (even for Geometry-type of problem).
Hope this help the GMATClub community.