BTGmoderatorDC wrote: ↑Sun Jun 07, 2020 6:42 pm
Screen-Shot-2016-11-22-at-5.28.41-PM-e1479816030549.png
In the triangle above, what is the measure of Angle CDB?
(1) Angle CAB = Angle ACB = 30°
(2) AB = BC = BD
OA
A
Source: e-GMAT
Let's take each statement one by one.
(1) Angle CAB = Angle ACB = 30°
Given that Angle CAB = Angle ACB = 30°, in the ∆ABC, we have Angle ABC = 180 – 30 – 30 = 120º.
Also, since Angle ACD = 90º and Angle CAB = 30º, we have Angle BCD = 90 – 30 = 60º
Also, since Angle ABC = 120º, we have Angle CBD = 60º.
So, in ∆BCD, Angle CDB = 180 – 60 – 60 = 60º
Sufficient.
(2) AB = BC = BD
Since we do not have any measure of angles, we cannot get the unique value of Angle CDB. Insufficient.
The correct answer:
A
Hope this helps!
-Jay
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