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# Analyzing related rates problems: equations

AP.CALC: CHA‑3 (EU), CHA‑3.D (LO), CHA‑3.D.1 (EK), CHA‑3.D.2 (EK)

## Problem

Zhenghao was given this problem:
The radius r, left parenthesis, t, right parenthesis of a sphere is decreasing at a rate of 1 meter per hour. At a certain instant t, start subscript, 0, end subscript, the radius is 4 meters. What is the rate of change of the volume V, left parenthesis, t, right parenthesis of the sphere at that instant?
Which equation should Zhenghao use to solve the problem?