The length of the actual pen is 20 meters.
The scale drawing is a reduced form of an original image. The scale drawing is reduced by constant dimensions. In this question, the scale is 5cm : 2m. This means that on the scale drawing, 5cm represents 2m.
Length of the actual pen = (length of the pen on the scale drawing x 2m) / 5cm
(50 x 2) / 5
100 / 5
= 20 m
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