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Ch. 3 - Derivatives
Briggs - Calculus: Early Transcendentals 3rd Edition
Briggs3rd EditionCalculus: Early TranscendentalsISBN: 9780136847243Not the one you use?Change textbook
Chapter 3, Problem 3.11.37

Water is drained out of an inverted cone that has the same dimensions as the cone depicted in Exercise 36. If the water level drops at 1 ft/min, at what rate is water (in ft³/min) draining from the tank when the water depth is 6 ft? 

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1
First, identify the relationship between the volume of the cone and its dimensions. The formula for the volume of a cone is V = (1/3)πr²h, where r is the radius and h is the height.
Since the cone is inverted and the water level drops, we need to express the radius r in terms of the height h. Use the similar triangles property from the cone's dimensions to find this relationship.
Differentiate the volume formula with respect to time t to find the rate of change of the volume, dV/dt. Use the chain rule to differentiate, considering that both r and h are functions of time.
Substitute the given rate of change of the height, dh/dt = -1 ft/min, into the differentiated equation. Also, substitute the height h = 6 ft to find the rate at which the volume is changing at that specific height.
Solve the resulting equation for dV/dt, which represents the rate at which water is draining from the tank in ft³/min.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Related Rates

Related rates involve finding the rate at which one quantity changes in relation to another. In this problem, we need to determine how the volume of water in the cone changes as the water level drops. This requires applying the chain rule of differentiation to relate the rates of change of the water depth and the volume.
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Volume of a Cone

The volume of a cone is calculated using the formula V = (1/3)πr²h, where r is the radius of the base and h is the height. In this scenario, as the water level decreases, both the height and the radius of the water's surface change, which affects the volume. Understanding this relationship is crucial for applying the related rates concept.
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Differentiation

Differentiation is a fundamental concept in calculus that involves finding the derivative of a function, which represents the rate of change of that function. In this context, we will differentiate the volume formula with respect to time to find the rate at which the volume of water is draining from the cone as the water level drops.
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