Math Problem Statement

The volume V of a cylinder is computed using the values 3.8m for the radius and 6.3m for the height. Use the linear approximation to estimate the maximum error in V if each of these values has as a possible error of at most 8%.

Solution

To solve this problem, we use the concept of linear approximation (also called the differential approximation) to estimate the maximum error in the volume of a cylinder due to potential errors in the radius and height.

Formula for the Volume of a Cylinder

The volume VV of a cylinder is given by: V=πr2hV = \pi r^2 h where:

  • rr is the radius,
  • hh is the height,
  • π3.1416\pi \approx 3.1416.

Step 1: Find the Differential of the Volume

We need to find the differential dVdV of the volume function V=πr2hV = \pi r^2 h. To do this, we use partial derivatives with respect to rr and hh.

The total differential dVdV is given by: dV=Vrdr+VhdhdV = \frac{\partial V}{\partial r} dr + \frac{\partial V}{\partial h} dh

First, we compute the partial derivatives: Vr=2πrhandVh=πr2\frac{\partial V}{\partial r} = 2\pi r h \quad \text{and} \quad \frac{\partial V}{\partial h} = \pi r^2

Thus, the total differential is: dV=2πrhdr+πr2dhdV = 2\pi r h \, dr + \pi r^2 \, dh

Step 2: Estimate the Maximum Error

Given that the maximum errors in rr and hh are both 8%, we can express these errors as: dr=0.08randdh=0.08hdr = 0.08r \quad \text{and} \quad dh = 0.08h

Substitute these into the differential: dV=2πrh(0.08r)+πr2(0.08h)dV = 2\pi r h (0.08r) + \pi r^2 (0.08h) Simplifying: dV=0.16πr2h+0.08πr2hdV = 0.16\pi r^2 h + 0.08\pi r^2 h dV=0.24πr2hdV = 0.24\pi r^2 h

Step 3: Calculate the Approximate Maximum Error in the Volume

Now, substitute the given values r=3.8mr = 3.8 \, \text{m} and h=6.3mh = 6.3 \, \text{m} into the equation for dVdV:

dV=0.24π(3.8)2(6.3)dV = 0.24 \pi (3.8)^2 (6.3)

First, compute r2r^2 and then multiply by hh: r2=(3.8)2=14.44r^2 = (3.8)^2 = 14.44 r2h=14.44×6.3=90.972r^2 h = 14.44 \times 6.3 = 90.972

Now, calculate the error: dV=0.24×π×90.9720.24×3.1416×90.97265.044dV = 0.24 \times \pi \times 90.972 \approx 0.24 \times 3.1416 \times 90.972 \approx 65.044

Thus, the approximate maximum error in the volume is: dV65.04m3dV \approx 65.04 \, \text{m}^3

Final Answer:

The maximum error in the volume of the cylinder, based on the 8% possible errors in both radius and height, is approximately 65.04 cubic meters.


Would you like a detailed explanation of any part of this process or have other questions? Here are some related questions you might find helpful:

  1. How do you apply linear approximation to other geometric shapes?
  2. How do you calculate the actual percentage error in the volume of a cylinder?
  3. How does the size of the error in radius and height affect the overall volume error?
  4. What are the advantages of using linear approximation in practical applications?
  5. How can you extend this approach to multi-variable functions with more than two variables?

Tip: When dealing with measurements and errors, remember that the linear approximation works well when the errors are small. Larger errors may require higher-order approximations.

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Math Problem Analysis

Mathematical Concepts

Linear Approximation
Differentiation
Volume of a Cylinder
Error Estimation

Formulas

V = πr^2h
dV = 2πrh dr + πr^2 dh

Theorems

Differential Approximation

Suitable Grade Level

Grades 11-12