Answer:
r = 16 units
Step-by-step explanation:
From the figure attached,
AB is the tangent drawn from a point A to the circle C.
BC = r [Radius of the circle]
Length of AC = (18 + r)
AB = 30
By the property of a tangent drawn to a circle,
"Radius of a circle and tangent are perpendicular to each other"
AB ⊥ BC
By applying Pythagoras theorem in ΔABC,
AB² + BC² = AC²
(30)² + r² = (r + 18)²
900 + r² = r² + 36r + 324
36r = 900 - 324
r =
r = 16 units