Question:

If the angle of intersection at a point where the two circles with radii 5cm and 12cm intersect is 90°, then the length (in cm) of their common chord is?

60/13

120/13

135

120/13

Correct option is B. 120/13
Let length of common chord = 2x
25 - x² + 144 - x² = 13
After solving
x = 12√5/13
2x = 120/13