The radii of two circles are 4 cm and 7 cm and the distance between their centres is 12 cm. Find the length of the direct common tangent to the circles.
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. 3√15 cm.
Formula used:
Length of the direct common tangent = √(Distance between their centres)2 - (R2 - R1)2 ---- (1)
Calculations:
Using equation (1), we get
⇒ Length = √(12)2 - (7 - 4)2
⇒ √144 - 9 = √135
⇒ 3√15 cm