Question

What is the order of rotational symmetry of an equilateral triangle?

Answer 1

Let us rotate an equilateral triangle ABC through ${120}^o,{240}^o$ and ${360}^o$ to attain the positions Shown in fig1, fig2, fig3 and fig4 respectively.
Clearly, each of the three times, the figure fits onto itself.
So, it has a rotational symmetry of order 3.