(a) 96 cm2
Since the diagonals of a rhombus bisect each other at right angles.
In Δ AOB, BO2 = \(\sqrt{AB^2-AO^2}\)
= \(\sqrt{100-64}\) cm
= \(\sqrt{36}\) = 6 cm
∴ The other diagonal = 2 × 6 cm = 12 cm
∴ Area of the rhombus = \(\frac12\) × 16 cm × 12 cm = 96 cm2.