Question : In the given figure, PAB is a secant and PT is a tangent to the circle from P. If PT = 5 cm, PA = 4 cm and AB = x cm, then x is:
Option 1: $\frac{4}9$ cm
Option 2: $\frac{9}4$ cm
Option 3: 5 cm
Option 4: $\frac{2}{3}$ cm
Correct Answer: $\frac{9}4$ cm
Solution :
Given, PT = 5 cm, PA = 4 cm and AB = x cm,
Secant PB = (4 + x) cm.
As we know when a tangent and secant are drawn from a common point outside the circle, then the square of the tangent is equal to the product of the length of the part of the secant outside the circle and the entire secant.
⇒ PA × PB = PT
2
⇒ 4 (4 + x) = 5
2
⇒ 16 + 4x = 25
⇒ 4x = 9
⇒ x = $\frac{9}{4}$ cm
Hence, the correct answer is $\frac{9}{4}$ cm.
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