Question

Find the value of the unknown x in the following diagrams:

Answer 1

The sum of all interior angles of a triangle is 180°. By using this property, these problems can be solved as follows.

(i) x + 50° + 60° = 180°

x + 110° = 180°

x = 180° − 110° = 70°

(ii) x + 90° + 30° = 180°

x + 120° = 180°

x = 180° − 120° = 60°

(iii) x + 30° + 110° = 180°

x + 140° = 180°

x = 180° − 140° = 40°

(iv) 50° + x + x = 180°

50° + 2x = 180°

2x = 180° − 50° = 130°

(v) x + x + x = 180°

3x = 180°

(vi) x + 2x + 90° = 180°

3x = 180° − 90° = 90º