Mathematics

The key insight is to simplify $\sqrt{20}$ before multiplying. Notice that $20 = 4 \times 5$, so $\sqrt{20} = \sqrt{4 \times 5} = \sqrt{4} \cdot \sqrt{5} = 2\sqrt{5}$. Now your product becomes $\sqrt{5} \times 2\sqrt{5}$, which is just $2 \times (\sqrt{5})^2 = 2 \times 5 = 10$. The core concept is recognizing when you can factor out perfect squares from under a radical.

The key insight is to simplify $\sqrt{20}$ before multiplying. Notice that $20 = 4 \times 5$, so $\sqrt{20} = \sqrt{4 \times 5} = \sqrt{4} \cdot \sqrt{5} = 2\sqrt{5}$. Now your product becomes $\sqrt{5} \times 2\sqrt{5}$, which is just $2 \times (\sqrt{5})^2 = 2 \times 5 = 10$. The core concept is recognizing when you can factor out perfect squares from under a radical.