Answer:
168 cm²
Explanation:
The area of a quadrilateral with diagonals that intersect at right angles is half the product of the lengths of the diagonals. A rhombus is one such quadrilateral, so the area of this one is ...
A = 1/2(d1)(d2)
A = (1/2)(21 cm)(16 cm) = 168 cm²
The area of the rhombus is 168 cm².