Question

What is the measure of angle ABC in the figure below?

A: 15
B: 30
C: 45
D: 90
E: 15
F: Cannot be determined

Answer 1

∠ADB = 180° - 90° - 45° = 45°
∠BDC = 45° (Alternate angles)
∠DBC = 180° - 90° - 45° = 45°

∠ABC = 45° + 45° = 90°
Answer is D.

Answer 2

The answer is D. Because angles BAD and BCD are shown to be right angles (90 degrees), quadrilateral ABCD is a square, which means all of it's angles are 90 degrees.