Question

Find the value of unknown angle x in the following figures :

Answer 1

Sum of all angles of a triangle is 180°.

(i) x + 60° + 85° = 180°
⇒ x + 145° = 180°
⇒ x = 180° – 145° = 35°

(ii) x + 40° + 20° = 180°
⇒ x + 60° = 180°
⇒ x = 180° – 60° = 120°

(ii) x + 40° + 90° = 180°
⇒ x + 130° = 180°
⇒ x = 180° – 130° = 50°

(iv) x + x + x = 180°
⇒ 3x = 180°
⇒ x = 180°/3 = 180°