Two adjacent sides of a parallelogram are 51cm and 37cm. One of its diagonals is 20cm, then its area is:
Let ABCD be the given parallelogram as shown above.
Diagonal of a parallelogram divides it into two triangles of equal areas.
Hence, area (parallelogram ABCD) =2 area (ΔBCD)
Let us calculate the area of ΔBCD by using Heron’s Formula.
Area of ΔBCD
= 17 × 2 × 3 × 3 =306 cm2
So, area of parallelogram ABCD =2×306 cm2=612 cm2