# Related rates intro

Practice your understanding of related rates.
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### Problem

The radius of the base of a cylinder is decreasing at a rate of 12 kilometers per second.
The height of the cylinder is fixed at 2, point, 5 kilometers.
At a certain instant, the radius is 40 kilometers.
What is the rate of change of the volume of the cylinder at that instant (in cubic kilometers per second)?
Please choose from one of the following options.
The volume of a cylinder with radius r and height h is pi, r, start superscript, 2, end superscript, h.