Question

As shown in the above figure, the two sides of the regular Hexagon when extended meet at the intersection of the lines $l$ and $m$. If the measure of angle$A$ is 120 degree, then the measure of angle $B$, in degree, is:

• A. 30
• B. 60
• C. 90
• D. 140

Answer 1

Answer: (B)

60

Since it is regular hexagon so all angles must be 120 degree. Exterior angle will be 180-120=60 degree.

We have two exterior angle measure 60 degree so the triangle formed must be equilateral triangle. So, all its angles are ${60}^{\circ }$

Now, the measure of angle B should be equal to the measure of the angle that is vertically opposite to it (and is an interior angle of our equilateral triangle shown in figure) that's ${60}^{\circ }$ So the correct answer will be Option B