Here's how to simplify the square root of 20:

1. Find the largest perfect square that divides 20:

* The largest perfect square that divides 20 is 4 (because 4 x 5 = 20).

2. Rewrite the radical:

* √20 = √(4 x 5)

3. Apply the product property of radicals:

* √(4 x 5) = √4 x √5

4. Simplify:

* √4 x √5 = 2√5

Therefore, the simplified form of √20 is 2√5.