Question

Which of the following angle construction is not possible with a ruler and a compass?

• A. 90 degree
• B. 30 degree
• C. 80 degree
• D. 120 degree

Answer 1

The correct option is C

80 degree

90, 30 and 120 degrees angles are the standard one to construct. For these a ruler and a compass is used. Using a compass and arcs made by it, one can construct, 90, 60, 30 or 120 degree angle easily. 80 degree angle is not a half angle of any standard angle, so it cannot be constructed using a compass and ruler.