# 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 ______. - Mathematics

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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 ______.

• 3 cm

• 6 cm

• 9 cm

• 1 cm

#### Solution

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 6 cm.

Explanation:

Given,

OA = 4 cm, OB = 5 cm

And, OA ⊥ BC

Therefore, OB2 = OA2 + AB2

⇒ 52 = 42 + AB2

⇒ AB = sqrt(25 - 16) = 3 cm

⇒ BC = 2AB = 2 × 3 cm = 6 cm

Concept: Tangent to a Circle
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#### APPEARS IN

NCERT Mathematics Exemplar Class 10
Chapter 9 Circles
Exercise 9.1 | Q 1 | Page 102
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