Let us rotate an equilateral triangle ABC through 120o, 240o and 360o to attain the positions Shown in fig 1, fig 2, fig 3 and fig 4 respectively.
![](https://www.sarthaks.com/?qa=blob&qa_blobid=14306505680394080899)
Clearly, each of the three times, the figure fits onto itself.
So, it has a rotational symmetry of order 3.