A parallelogram has sides 60 m and 40 m and one of the diagonal is 80 m long. Then its area is?

• A. 480 sq. m
• B. 320 sq. m
• C. 450 ? 15 sq. m
• D. 600? 15 sq. m

Answer: (D)

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