Q. 94.2( 185 Votes )

Top surface of a raised platform is in the shape of a regular octagon as shown in the figure. Find the area of the octagonal surface.


Answer :

Given: Octagon having eight equal sides, each 5 m


Construction: Divided the octagon in 3 figures, two trapeziums whose parallel and perpendicular sides are 11 m and 4 m respectively and third figure is rectangle having length and breadth 11 m and 5 m respectively.



Now Area of two trapeziums = 2 x 1/2 × (a + b) h


= (11 + 5) × 4


= 64 sq. m


And Area of rectangle = length × breadth


= 11 × 5


= 55 sq. m


Total area of octagon = 64 + 55


= 119 sq. m


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