The scale from the drawing means ...
... drawing size : life size = 3 : 1000
This can be turned around to get ...
... life size : drawing size = 1000 : 3
I find this form more convenient to use in a proportion:
... actual length / drawing length = 1000 / 3
Multiplying by "drawing length", we get ...
... actual length = (drawing length)·(1000/3)
This will be true for both drawing lengths.
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... Pool length = (15 cm)·1000/3 = 5000 cm = 50 m
... Pool width = (7.5 cm)·(1000/3) = 2500 cm = 25 m
The area is the product of these dimensions:
... pool area = (50 m)·(25 m) = 1250 m²
