Equilateral and easy

The area of an equilateral triangle is given by $A=\dfrac{\sqrt{3}}{4}x^2$ where $x$ is the side length. Substituting, we get

$4=\dfrac{\sqrt{3}}{4}x^2$

$x^2=\dfrac{4 \cdot 4}{\sqrt{3}} \approx \boxed{3.03}$

An equilateral triangle of side-length 4 cm has an area of 1/2 * base * height = $1/2 * 4 * (2 * \sqrt{3})$ sq cm.

So to reduce this to an area of 4 sq cm, the side length must be divided by a factor of $\sqrt{\sqrt{3}}$ cm. Doing this results in a side length of 3.04 cm.