Calculating the Remaining Area of a Park

MathematicsGeometryMedium

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What is the total area of this?

This question includes visual content: The image shows a large irregular green polygon representing a park. It has a circular cut-out in the top-left corner (radius 14m), a square 'Fountain' ($5m imes 5m$), a rectangular 'Playground' (with segments measuring 20m, 28m, 7m, 5m), and an oddly shaped 'Flower garden' (with dimensions 11.5m, 7m, 7.94m, 15m). The overall boundary of the park is defined by sides measuring 46m, 50m, 60m, and 22m.

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Step by Step Written Solution

1
Step 1

Hi Keita, let's work through this composite area problem step by step by separating the large boundary from the cut out regions inside it.

Find the Total Shaded Area

We will calculate the area of the outer shape first, then subtract the areas of the empty regions.

2
Step 2

From the diagram, the outside boundary can be treated as a large rectangle with a triangular corner removed, and also a semicircular notch on the left side.

$$A_{outer}=A_{rectangle}-A_{triangle}-A_{semicircle}$$
$$60\times 64$$
$$\frac{1}{2}\times 14\times 42$$
$$\frac{1}{2}\pi\times 7^2$$
3
Step 3

The full height is fifty meters plus the fourteen meter semicircle diameter, giving a total height of sixty four meters.

4
Step 4

Now substitute the values into the outer area expression.

$$A_{outer}=3840-294-76.97$$
5
Step 5

So the outer shaded boundary has an area of about three thousand four hundred sixty nine square meters.

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Step 6

Next, let's find the area of the playground, which is an L shaped region.

Playground Area

$$A_{play}=A_{large\ rectangle}-A_{missing\ rectangle}$$
$$28\times 20-(28-5)\times 7$$
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Step 7

The large rectangle measures twenty eight by twenty, and the missing top right rectangle has width twenty three and height seven.

8
Step 8

Multiplying gives one hundred sixty one for the missing rectangle.

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About This Question

Subject
Mathematics
Topic
Geometry
Difficulty
Medium
Question Type
Open Ended

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