-
The radii of two concentric circles are 13 cm and 8 cm. AB is a diameter of the bigger circle and BD is a tangent to the smaller circle touching it at D and the bigger circle at E. Point A is joined to D. The length of AD is
-
- 20 cm
- 19 cm
- 18 cm
- 17 cm
- 20 cm
Correct Option: B
On the basis of question we draw a figure of two concentric circles with radii 13 cm and 8 cm ,
∠ODB = 90°
Here , OD = 8 cm and OB = 13 cm
∴ BD = √13² - 8²
BD = √169 - 64
BD = √105 cm
AE = 16 cm; ∠AED = 90°
AD = √AE² + DE²
AD = √256 + 105 = √361 = 19 cm
