The two adjacent sides of a parallelogram are 12 cm and 5 cm respectively. If one of the diagonals is 13 cm long, then what is the area of the parallelogram?

60 cm²

In the parallelogram ABCD,

The numbers 5, 12, 13 are triplet so angle D is 90°

This parallelogram is a rectangle.

Area of ABCD = product of sides = AD x CD

                     = 5 x 12 = 60 cm²