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 = 2×1/2(a+b)xh
= 2×1/2(11+5)x4=4×16=64cm²
And Area of rectangle = length x breadth
= 11 x 5 = 55m²
∴ Total area of octagon = 64 + 55 = 119 m²

Class 8 Maths Chapter 11 Exercise 11.2 Solution in Video

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