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Two circles of radii 17 cm and 8 cm are concentric. The length of a chord of greater circle which touches the smaller circle is
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- 15 cm
- 16 cm
- 30 cm
- 34 cm
- 15 cm
Correct Option: C
As per the given in question , we draw a figure of two concentric circles with centre O, 
According to the Question,
OC = radius of smaller circle = 8 cm.
OA = radius of larger circle = 17 cm.
AB = chord of larger circle
OC ⊥ AB
∴ AC = CB
From ∆ OAC,
AC = √OA² - OC² = √17² - 8²
AC = √(17 + 8)(17 - 8)
AC = √25 × 9 = 5 × 3 = 15 cm.
∴ AB = 2AC = 30 cm.
