Question

Lines a and b are parallel lines cut by transversal f.

Parallel lines a and b are cut by transversal f. At the intersection of lines f and b, the uppercase left angle is angle 4. At the intersection of lines f and a, the uppercase right angle is angle 1.

If , what is ?

20°
70°
110°
130°

Answer 1

110°

Reason: angle 1 is the corresponding angle to the upper-right angle at line b (the bottom intersection). At the bottom intersection, angle 4 (upper-left) and that upper-right angle form a linear pair, so they sum to 180°. Thus angle 1 = 180° − angle 4 = 180° − 70° = 110°.