A question on circles

Given that a lamp-post can light a surrounding circle of radius 100 m, what is the minimum number of such lamp-posts required to light a circular ground of radius 1000 m.

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This bound can be improved, since the optimal coverage of a plane involves hegaxonal packing, which reduces the effective area of each small circle by a factor of $\frac{3 \sqrt{3}}{2 \pi} \approx 0.82699$ so you would need at least 121 lamposts, and probably a few more.