Question

In the below fig, rays AB and CD intersect at O

Determine x when y =40

Answer 1

Given y = 40°, x = ?

`∠`AOC and `∠`BOC are linear pair of angles

`∠`AOC + `∠`BOC = 180°

⇒ 2x + y = 180°

⇒  2x + 40 = 180°

⇒ 2x = 140°

⇒ x = `(140°)/2`

⇒ y = 70°

Answer 2

Rays ABand CD intersect at point O.

Therefore, ∠AOCand ∠BOCform a linear pair.

Thus,

∠AOC +∠BOC = 180°

          2x +y =180°       (1)

On substituting y = 40°:

2x +y = 180°

2x + 40° = 180°

2x = 180°-40°

2x = 140°

`x = (140°)/2`

x = 70°