Question

Three straight lines are shown in the diagram.

Work out the size of angle a, b and c.
Give reasons for your answers.

Answer 1

A:50⁰

B:100⁰

C:30⁰

Explanation:

Angle A:

as you can see in the photo, there is a concave angle of A that is 310⁰.

Considering that a full angle is 360⁰, we can calculate A by subtracting the concave of A to the full 360⁰

360⁰-310⁰=50⁰

b:

by knowing that a flat angle is 180⁰, and the opposite of B is 80⁰, we subtract 80⁰ from 180⁰

180⁰-80⁰=100⁰

knowing that the sum of convex angles of any triangle is 180⁰, we already know A and B, C is missing.

so if we subtract A and B from 180⁰ we find C

180⁰-50⁰-100⁰=30⁰