Im trying to understand related rates here and im getting stuck at this word problem.

It says if V is the volume of a sphere with radius r, and the volume of the sphere decreases as the time passes. express dV/dt in terms of dr/dt. Describe the relationship in words.

I dont get what it means by dV/dt in terms of dr/dt, i know what the derivatives and related rates mean, but I have trouble connecting them to each other.