<|system|>
Find the distance between the foci of the ellipse \[x^2 + 4y^2 = 400.\]</s>.
<|user|>
Can you answer based on context?
<|assistant|>
Dividing by $400,$ we get \[\frac{x^2}{20^2} + \frac{y^2}{10^2} = 1.\]Thus, the length of the major and minor axes are $2 \cdot 20 = 40$ and $2 \cdot 10 = 20,$ respectively. Then the distance between the foci of the ellipse is $\sqrt{40^2 - 20^2} = 20\sqrt3.$