Question

In the diagram, ABC is a straight line.

Work out the size of the angle marked x.

Answer 1

x = 31°

Explanation:

since AB = BD then Δ ABD is isosceles with base angles congruent, so

∠ ADB = ∠ BAD = 62°

the sum of the 3 angle in Δ ABD = 180° , so

∠ ABD = 180° - 62° - 62° = 180° - 124° = 56°

∠ ABD and ∠ CBD are a linear pair and sum to 180° , so

56° + ∠ CBD = 180° ( subtract 56° from both sides )

∠ CBD = 124°

the 3 angles in Δ CBD sum to 180° , then

x + 124° + 25° = 180°

x + 149° = 180° ( subtract 149° from both sides )

x = 31°

Answer 2

See below

Explanation:

1 note the other angle at d = 62 ( isosceles triangle)

2 x = 180 - 62 - 62 -25