Circles of radii `36` and `9` touches externally. The radius of the circle which touches the two circles externally and also their common tangent is

Two circles of radius 1 and 4 touch each other externally.Another circle of radius r touches both circles externally and also one direct common tangent of the two circles.Then [(1)/(r)]=

Two circles with radii a and b respectively touch each other externally . Let c be the radius of a circle that touches these two circles as well as a common tangent to the circles. Then

Circles of radii 2,2,1 touch each other externally.If a circle of radius r touches all the three circles externally,then r is

Three circles of radii 1,2,3 touch other externally.If a circle of radiusr touches the three circles,then r is

The locus of the centre of a circle the touches the given circle externally is a _______