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A chord AB = 24 cm of the outer of two concentric circles touches the inner circle. The radii differ by 4 cm. Find the outer radius.

Class 10Tangent Lengths and IncirclesGeometry

A18 cm
B20 cm
C13 cm
D16 cm

Step-by-Step Solution

R^{2} - r^{2} = 1 2^{2} = 144

and

R - r = 4

, so

R + r = 144 \div 4 = 36. R = (36 + 4) /2 = 20

cm (inner radius 16 cm).

Answer: B) 20 cm

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