The Total solution for NCERT class 6-12
Area ofthe octagonal surface = area of trapezium ABCH + area of rectangle HCDG + areaof trapezium GDEFArea of trapezium ABCH = Area of trapezium GDEF= 1 (a+ b) × h= 1 (11+ 5) × 4= 1 ×16 × 4= 32 m2Area of rectangle HCDG = l × b = 11 m × 5 m = 55 m2Area of the octagonal surface = 32 m2 +55 m2 +32 m2 =119 m2Hence, the required area = 119 m2.