question_answer

Two circles of radii \[R\] and \[r\] touch each other externally and \[PQ\] is the direct common tangent. Then \[P{{Q}^{2}}\] is equal to:

A) \[R-r\]                           

B) \[R+r\]

C) \[2Rr\]              

D)        \[4Rr\]  

Correct Answer: D

Solution :

\[P{{Q}^{2}}={{(R+r)}^{2}}-{{(R-r)}^{2}}=4Rr=4Rr\]