Calculate the Unmarked Angle: Finding the Missing Value in a 160° Ray Diagram

Question

Calculate the size of the unmarked angle:

00:00 Find the value of the empty angle

00:03 A straight angle equals 180

00:06 Therefore subtract the known angle from it to find the empty angle

00:09 And this is the solution to the question

The unmarked angle is adjacent to an angle of 160 degrees.

Remember: the sum of adjacent angles is 180 degrees.

Therefore, the size of the unknown angle is:

$180-160=20$