DRDO Multi tasking staff Model paper 2

If a, b and c are in continued - proportion, then
a, b, b, c are in proportion, that means a : b : : b : c
⇒ Product of extremes = Product of means
⇒ a × c = b × b
Here a = 9, c = 16
So,
⇒ 9 × 16 = b × b
⇒ b = 12