Question

two concentric circles radii 12 and 15 a chord of bigger circle becomes a tangent of smaller circle then the length of chord is​

Answer 1

in the circle with radius r1=12 and r2=15

In ∆OAP,we get

OA^2=OP^2+AP^2

15^2=12^2+AP^2

AP^2=225-144

=81

AP=√81

AP=9

AP+BP=AB

9+9=18