Two spherical balls lie on the ground touching. If one of the balls has a radius of 3 cm, and the point of contact is 5 cm above the ground, what is the radius of the other ball?  Choices:
A) 3 cm  B) 9 cm  C) 12 cm  D) 15 cm  E) none of the these
similar triangle properties..   2/r+3 = 3/r-3   giving r = 15.   Answer: 15 cm
<result>D</result>
Two spherical balls lie on the ground touching. If one of the balls has a radius of 3 cm, and the point of contact is 5 cm above the ground, what is the radius of the other ball?