Question bank / Lines, angles, and triangles

Math · Geometry and TrigonometryEasy

Points AA, BB, and CC lie on a line, with BB between AA and CC. Point DD does not lie on the line. The measure of angle ABDABD is (3x)∘(3x)^\circ, and the measure of angle DBCDBC is (2x)∘(2x)^\circ. What is the measure of angle ABDABD?

A

36∘36^\circ

B

72∘72^\circ

C

108∘108^\circ

D

144∘144^\circ

Show answer and explanation

Answer: C

Angles ABDABD and DBCDBC form a linear pair, so their measures sum to 180∘180^\circ: 3x+2x=1803x + 2x = 180. So x=36x = 36, and angle ABDABD measures 3(36)=108∘3(36) = 108^\circ.

Choice A is the value of xx, not the measure of angle ABDABD.

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