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Question

There is a rectangular garden of 220 metres × 70 metres. A path of width 4 metres is built around the garden. What is the area of the path?

The correct answer is

2384 metre2

Understanding the Problem: Rectangular Garden and Path Area

The problem asks us to calculate the area of a path built around a rectangular garden. We are given the dimensions of the garden and the uniform width of the path surrounding it.

Given Information:

  • Garden Length: 220 metres
  • Garden Width: 70 metres
  • Path Width: 4 metres

The path is built around the garden. This means the path forms a larger rectangle outside the garden. To find the area of the path, we need to find the area of the larger rectangle (garden plus path) and subtract the area of the inner rectangle (the garden itself).

Step-by-Step Calculation of the Path Area

Step 1: Calculate the Area of the Garden

The garden is a rectangle. The area of a rectangle is given by the formula: Area = Length × Width.

Area of Garden = Garden Length × Garden Width

\(\text{Area}_{\text{garden}} = 220 \text{ m} \times 70 \text{ m}\)

\(\text{Area}_{\text{garden}} = 15400 \text{ m}^2\)

Step 2: Calculate the Dimensions of the Garden Including the Path

Since the path of width 4 metres is built all around the garden, it adds 4 metres to each end of both the length and the width.

  • New Length (including path) = Garden Length + 2 × Path Width
  • New Width (including path) = Garden Width + 2 × Path Width

New Length = 220 m + 2 \(\times\) 4 m

New Length = 220 m + 8 m

New Length = 228 m

New Width = 70 m + 2 \(\times\) 4 m

New Width = 70 m + 8 m

New Width = 78 m

Step 3: Calculate the Area of the Garden Including the Path

This larger area is also a rectangle with the new calculated dimensions.

Area (Garden + Path) = New Length × New Width

\(\text{Area}_{\text{total}} = 228 \text{ m} \times 78 \text{ m}\)

To calculate \(228 \times 78\):

200 20 8
70 14000 1400 560
8 1600 160 64

Summing the values: \(14000 + 1400 + 560 + 1600 + 160 + 64 = 17784\)

\(\text{Area}_{\text{total}} = 17784 \text{ m}^2\)

Step 4: Calculate the Area of the Path

The area of the path is the difference between the total area (garden plus path) and the area of the garden alone.

Area of Path = Area (Garden + Path) - Area of Garden

\(\text{Area}_{\text{path}} = \text{Area}_{\text{total}} - \text{Area}_{\text{garden}}\)

\(\text{Area}_{\text{path}} = 17784 \text{ m}^2 - 15400 \text{ m}^2\)

\(\text{Area}_{\text{path}} = 2384 \text{ m}^2\)

Conclusion

The area of the path built around the rectangular garden is 2384 square metres.

Revision Table: Rectangular Area Calculations

Component Length Width Area
Garden 220 m 70 m \(220 \times 70 = 15400\) m<sup>2</sup>
Garden + Path \(220 + 2 \times 4 = 228\) m \(70 + 2 \times 4 = 78\) m \(228 \times 78 = 17784\) m<sup>2</sup>
Path Only N/A N/A \(17784 - 15400 = 2384\) m<sup>2</sup>

Additional Information: Areas of Rectangular Shapes

Calculating areas involving paths around rectangular shapes is a common geometry problem. The key idea is to consider the shapes as nested rectangles. The area of the path is the area of the outer rectangle minus the area of the inner rectangle.

  • When a path is *outside* a rectangle, both the length and width of the outer rectangle are increased by twice the path width.
  • When a path is *inside* a rectangle, both the length and width of the inner rectangle are decreased by twice the path width. The area of the path would then be the area of the outer rectangle minus the area of the inner rectangle.

Understanding how the path width affects the overall dimensions is crucial for accurately calculating the areas.

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Important Questions from Plane Figures

  1. If length of a rectangle is increased to its three times and breadth is decreased to its half, then the ratio of the area of given rectangle to the area of new rectangle is:

  2. The width of the path around a square field is 4.5 m and its area is 105.75 m 2. Find the cost of fencing the field at the rate of Rs. 100 per meter.

  3. What is the area of the square (in cm 2) whose vertices lie on a circle of radius 5 cm?

  4. The circumcentre of an equilateral triangle is at a distance of 3.2 cm from the base of the triangle. What is the length (in cm) of each of its altitudes?

  5. The perimeter of a circular lawn is 1232 m. There is 7 m wide path around the lawn. The area (in m 2) of the path is:

    Take \(\left(\pi=\frac{22}{7}\right)\)

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