Here is a map showing the Serpentine Lake in London. It is claimed that the Serpentine covers an area of \(40\) acres. How can you test this claim?
Getting started
For a start, there is a question about what is meant by the “Serpentine Lake” in the claim. Technically the Serpentine is only the part to the east of the bridge. The other part of the lake is called the Long Water. How can we decide whether the claim is talking about the whole lake, or just the part to the east of the bridge?
Use a rectangle to approximate the part of the lake to the east of the bridge.
What is the scale on the map?
How big is an acre?
We can approximate the part of the lake to the east of the bridge as a rectangle. Using the scale on the map, the rectangle is approximately \(\quantity{850}{m}\) by \(\quantity{150}{m}\) or \(\quantity{127\,500}{m^2}.\) An acre is approximately \(\quantity{4047}{m^2}\), so the area of the part of the lake which is to the east of the bridge is only about \(32\) acres. Therefore we can assume that the \(40\) acre claim is about the whole lake.
