Chord AB and diameter CD of a circle meet at the point P, outside the circle when produced. If PB = 8 cm, AB = 12 cm and the distance of P from the centre of the circle is 18 cm, the radius (in cm) of the circle is closest to :

12.8

By using secant property :-

PA × PB = PC × PD

Let us consider that , Radius of circle = a cm

( 12 + 8 ) × 8 = ( 18 - a ) × ( 18 + a )

160 = 18² - a²

a² + 160 = 324

a² = 164

a = 4√41

= 12.8