When a uniform flat plate of known total weight is perforated with holes, the weight removed is proportional to the fraction of the plate's total area that the holes occupy, since the plate has uniform thickness and density (mass is proportional to area for a fixed thickness/material).
The plate measures 5 m x 2 m = 500 cm x 200 cm, giving a total area of 500 x 200 = 100,000 cm^2,...
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