Two circles are having radii 9 cm and 12 cm. The distance between their centres is 15 cm. What is the length (in cm) of their common chord?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. 14.4
AB2 + BC2 = AC2
∠ABC = 90o
Draw perpendicular BD:
Area of △ABC = 1/2 × AB × BC = 1/2 × AC × BD
⇒ 9 × 12 = BD × 15
⇒ BD = 7.2 cm
Hence,
BE = 2BD = 2 × 7.2 = 14.4 cm