A secant PAB is drawn from an external point P to the circle with the centre at O, intersecting it at A and B. If OP = 17 cm, PA = 12 cm and PB = 22.5 cm, then the radius of the circle is:
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Correct answer: D
Explanation
The correct answer is option 4 i.e. cm.
The product of one whole secant segment and its external segment is equal to the product of the other whole secant segment and its external segment.

OP = 17 cm, PA = 12 cm and PB = 22.5 cm
Here, OD = OC = r cm (Radius)
So, PA × PB = PC × PD
⇒ PA × PB = (OP - OC)(OP + OD)
⇒ 12 × 22.5 = (17 - r)(17 + r) = 172 - r2
⇒ 270 = 289 - r2
⇒ r2 = 289 - 270 = 19
⇒ r = √19
Therefore, the radius of the circle is √19 cm.