Question

Two spheres, of radius 8 and 2, are resting on a plane table top so that they touch each other. How far apart are their points of contact with the plane table top?

• A. 6
• B. 7
• C. 8
• D. $8\sqrt{2}$
• E. 9

Answer 1

Answer: (C)

8

• The distance between centers is $8+2=10$
• the vertical distance is $8-2=6$
• Let the horizontal distance be $h$
• We have $h^2={10}^2-6^2=100-36=64$ , which implies $h=8$