Math Problem Statement

A cube grows at a rate of 8 m³/min. How fast are the sides of the cube increasing when the sides are 6 m each?

Solution

To solve this problem, we are tasked to determine how fast the sides of the cube are increasing when the volume of the cube grows at 8 m³/min, and the side length of the cube is 6 m.


Step-by-Step Solution

  1. Volume of a Cube: The volume VV of a cube is given by: V=s3V = s^3 where ss is the side length of the cube.

  2. Differentiate with respect to time tt: To relate the rate of change of volume dVdt\frac{dV}{dt} with the rate of change of the side length dsdt\frac{ds}{dt}, differentiate both sides of V=s3V = s^3 with respect to tt: dVdt=3s2dsdt.\frac{dV}{dt} = 3s^2 \frac{ds}{dt}.

  3. Substitute Known Values:

    • The rate of change of volume is dVdt=8m3/min\frac{dV}{dt} = 8 \, \text{m}^3/\text{min}.
    • The side length is s=6ms = 6 \, \text{m}.

    Plug these values into the equation: 8=3(62)dsdt.8 = 3(6^2) \frac{ds}{dt}.

  4. Simplify and Solve for dsdt\frac{ds}{dt}:

    • First, calculate 62=366^2 = 36: 8=3(36)dsdt.8 = 3(36) \frac{ds}{dt}.
    • Simplify 3×36=1083 \times 36 = 108: 8=108dsdt.8 = 108 \frac{ds}{dt}.
    • Solve for dsdt\frac{ds}{dt} (divide both sides by 108): dsdt=8108.\frac{ds}{dt} = \frac{8}{108}.
    • Simplify: dsdt=227.\frac{ds}{dt} = \frac{2}{27}.
  5. Final Answer: The rate at which the sides of the cube are increasing is: dsdt=227m/min.\frac{ds}{dt} = \frac{2}{27} \, \text{m/min}.


Conclusion:

When the side length of the cube is 6 meters, the sides are increasing at a rate of 227m/min\frac{2}{27} \, \text{m/min}.


Do you want me to explain this step further or clarify any part?

Related Questions:

  1. How does the rate of change of the side length depend on the volume growth rate?
  2. What happens to dsdt\frac{ds}{dt} if ss increases to 10 m?
  3. How would the problem change if the cube’s volume grew at 12m3/min12 \, \text{m}^3/\text{min}?
  4. Can you derive a general formula for dsdt\frac{ds}{dt} in terms of dVdt\frac{dV}{dt} and ss?
  5. What is the geometric interpretation of this problem?

Tip:

When solving related rates problems, always differentiate the given equation with respect to time tt, apply the chain rule carefully, and substitute known values to isolate the desired rate.

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Math Problem Analysis

Mathematical Concepts

Geometry
Differentiation
Related Rates

Formulas

V = s³
dV/dt = 3s²(ds/dt)

Theorems

Chain Rule

Suitable Grade Level

Grades 10-12