Question

If radii of two concentric circles are 4 cm and 5 cm, then the length of each chord of one circle which is tangent to the other circle is

(A) 3 cm (B) 6 cm

(C) 9 cm (D) 1 cm

Answer 1

 (B) 6 cm

According to the question,

OA = 4cm, OB = 5cm

And, OA ⊥ BC

Therefore, OB² = OA² + AB²

⇒ 5² = 4² + AB²

⇒ AB = √(25 – 16) = 3cm

⇒ BC = 2AB = 2 × 3cm = 6cm