AP EAMCET2010MathematicsCircle
The length of the common chord of the circles of radii 15 and 20, whose centres are 25 unit of distance apart, is
Options
- A12
- B16
- C24
- D25
Correct answer
C. 24
Step-by-step solution
Given, r₁=15 unit r₂=20 unit C₁ C₂=25 unit Let A C₂ D= Then, in right angled triangle A D C₂ , A D=r₂ A D r₂ = ...(i) Now, in right angled triangle A D C₁A D=r₁ (90- ) A D r₁ = ...(ii) On squaring and adding Eqs. (i) and (ii), we get A D^2 [ 1 r₁^2 + 1 r₂^2 ]=1 A D^2 ( r₁^2+r₂^2 r₁^2 r₂^2 )=1 A D^2= r₁^2 r₂^2 r₁^2+r₂^2 A D^2= 225 400 225+400 A D= 15 20 25 =12 Thus, length of common chord =2 A D=2 12=24 unit