To find what percent of the park is the playground, you can use the following formula:
\[ \text{Percent} = \left( \frac{\text{Area of Playground}}{\text{Area of Park}} \right) \times 100 \]
Plugging in the values:
\[ \text{Percent} = \left( \frac{80}{400} \right) \times 100 \]
Calculating this gives:
\[ \text{Percent} = 0.2 \times 100 = 20% \]
Thus, the playground is 20% of the park.