The distance between the centres of two circles of radius 4 cm and 2 cm is 10 cm. The length (in cm) of a transverse common tangent is.

12 8 10 18

8

Length of transverse common tangent = \(\sqrt {d^2-(r_1+r_2)^2}\) = \(\sqrt {(10)^2-(2+4)^2}\) = \(\sqrt {100-36}\) = 8 cm