## Algebra: A Combined Approach (4th Edition)

Take the sum of all the sides. $\sqrt {20} + \sqrt {8}$ Approximate the square roots based on the nearest perfect squares. $\sqrt {20}\approx4.4$ because it is between $\sqrt {16}$ and $\sqrt {25}$ (between 4 and 5). $\sqrt {8}\approx2.9$ because it is between $\sqrt{4}$ and $\sqrt {9}$ (between 2 and 3). so... $\sqrt {20} + \sqrt {8}\approx4.4+2.9\approx7$.