If a chord of a circle of radius 5 cm is a tangent to another

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If a chord of a circle of radius 5 cm is a tangent to another circle of radius 3 cm, both the circles being concentric, then the length of the chord is

1. 10 cm
2. 12.5 cm
3. 8 cm
4. 7 cm

Correct Option: C

As per the given in question , we draw a figure of two concentric circles with centre O,

AC = √AO² - OC²
AC = √5² - 3²
AC = √25 - 9
AC = √16 = 4 cm
∴ AB = 2 × 4 = 8 cm