Side of regular octagon = 5 cm

Area of trapezium ABCH = Area of trapezium DEFG

Area pf tra[ezium ABCD

Area of rectangle HGDC = 11 × 5 = 55 m^{2}

Area of octagon = Area of trapezium ABCH + Area of trapezium DEFG + Area of rectangle HGDC

= 32 m^{2} + 32 m^{2} + 55 m^{2} = 119 m^{2}