Related rate of a melting cube's side length
An ice cube is melting. Its shape remains a cube at all times, and its volume is decreasing at a constant rate of .
Let denote the side length of the cube (in cm) at time (in minutes), so that the volume is . Given that , find the rate at which the side length is changing, , at the instant when cm.
Hint
Differentiate implicitly with respect to using the chain rule to relate and , then substitute the known values and .
Step-by-step solution
Start with the volume formula for a cube, , where both and are functions of time . Differentiate both sides with respect to using the chain rule: . This equation relates the rate of change of volume to the rate of change of side length at any instant.
Substitute the known values (volume decreasing) and into the equation: . Solving for gives cm/min, meaning the side length is decreasing at a rate of cm per minute.
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