# Spheres of radius $3$ and $5$ rest on a table and touch each other. How far away are the points that touch the table?

"Two spheres of radii 3 inches and 5 inches rest on a table and touch one another. How far apart are the points at which they touch the table?

I get 3 + $\sqrt{21}$, but the book states the result as 2$\sqrt{15}$.

To solve the problem, I draw a line between the center of the small circle to a point on the radius of the big circle. I then work my way through with the Pythagorean theorem.

Any hints?