AB = 60 m, BC = 40 m and AC = 80 m ? s = (60 + 40 + 80 ) / 2 m = 90 m (s-a) = 90 - 60 = 30 m, (s-b) = 90 - 40 = 50 m and (s-c) = 90 - 80 = 10 m? Area of ? ABC = ?s(s-a)(s-b)(s-c) = ?90 x 30 x 50 x 10 m2= 300?15 m2? Area of parallelogram ABCD = 2 x area of ? ABC = 600?15 m2