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Mathematics

A rectangular plot of land measures 45 m x 30 m. A boundary wall of height 2.4 m is built all around the plot at a distance of 1 m from the plot. Find the area of the inner surface of the boundary wall.

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Answer

Given:

The boundary wall is built all around the rectangular plot at a distance of 1 meter, which means the wall forms a larger rectangle around the plot as shown in the figure below:

A rectangular plot of land measures 45 m x 30 m. A boundary wall of height 2.4 m is built all around the plot at a distance of 1 m from the plot. Find the area of the inner surface of the boundary wall. Area and Perimeter of Plane Figures, Concise Mathematics Solutions ICSE Class 9.

Dimensions of the outer rectangle (including the boundary wall):

Length of the outer rectangle = (45 + 1 + 1) m = 47 m

Width of the outer rectangle = (30 + 1 + 1) m = 32 m

Perimeter of the outer rectangle = 2(length + breadth)

= 2(47 + 32)

= 2 x 79 = 158 m

Area of the inner surface of the boundary wall is the perimeter of the outer rectangle multiplied by the height of the wall.

Inner surface area of boundary wall = Perimeter of outer rectangle x height of wall

= 158 m x 2.4 m

= 379.2 m2

Hence, the area of the inner surface of the boundary wall is 379.2 m2.

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