Question

Which one of the following angles can not be constructed using compass and ruler?

• A. ${30}^{\circ }$
• B. ${18}^{\circ }$
• C. ${22.5}^{\circ }$
• D. ${75}^{\circ }$

Answer 1

The correct option is B ${18}^{\circ }$

We can draw ${60}^{\circ }$ and bisect it to get ${30}^{\circ }.$
Similarly, we can bisect ${45}^{\circ }$ and get ${22.5}^{\circ }.$
Also, we can draw ${60}^{\circ }$ and bisect ${30}^{\circ }$ to get ${75}^{\circ }.$
But, ${18}^{\circ }$ cannot be drawn using compass.