Question : In two circles centred at O and O’, the distance between the centres of both circles is 17 cm. The points of contact of a direct common tangent between the circles are P and Q. If the radii of both circles are 7 cm and 15 cm, respectively, then the length of PQ is equal to:
Option 1: 15 cm
Option 2: 17 cm
Option 3: 10 cm
Option 4: 22 cm
Correct Answer: 15 cm
Solution :
Length of direct common tangent =
Square of difference between radius of two circles =
Length of direct common tangent, PQ =
Hence, the correct answer is 15 cm.