Two circles of radii 25 cm and 9 cm, respectively, touch each other externally at the point P, AB is the direct common tangent of these two circles of center R and S respectively.  The length of AB is equal to?

15 cm 30 cm 34 cm 16 cm

30 cm

AB =\(\sqrt {d^2 - (r_2 - r_1)^2 }\) = \(\sqrt {34^2 - 16^2}\) = 30 cm