Find the area of an equilateral triangle with a side length of 10 cm.

Side length of the equilateral triangle, a = 10 cm

​$$\text{Area} = \frac{\sqrt{3}}{4} a^2$$​​

​$$\text{Area} = \frac{\sqrt{3}}{4}\times10^2\\ \ \\\text{Area}=\frac{\sqrt{3}}{4}\times100\\ \ \\ \text{Area} =25\sqrt{3}\ cm^2$$ 

Thus, correct option is (d).