Question 18
An ant crawls on the plane. It starts at point $A$ and crawls for 1 cm, then turns $60^\circ$ to the right; crawls for another 2 cm and again turns $60^\circ$ to the right; crawls for another 3 cm and turns $60^\circ$ to the right; crawls for another 4 cm and turns $60^\circ$ to the right; and finally it craws 5 cm and reaches $F$. What is the distance, in cm, between $A$ and $F$?