Math Problem Statement

An open-top, hollow plastic cylinder is to be made using 61 m² of plastic available. Find the height h, in meters, of the open-top cylinder to give the maximum volume. (Round to the nearest tenth)

Solution

The problem is asking us to find the height hh, in meters, of an open-top cylinder that maximizes the volume, given a surface area constraint of 61 square meters.

Analyzing the Problem:

  1. Surface Area Constraint: The surface area SS of an open-top cylinder is given by: S=πr2+2πrhS = \pi r^2 + 2\pi rh where:

    • rr is the radius of the base of the cylinder.
    • hh is the height of the cylinder.

    The equation consists of the area of the base (πr2\pi r^2) and the lateral surface area (2πrh2\pi rh).

  2. Volume of the Cylinder: The volume VV of the cylinder is given by: V=πr2hV = \pi r^2 h

  3. Given:

    • Total surface area SS is 61 square meters.
    • We need to find hh that maximizes VV.

Step-by-Step Solution:

  1. Express hh in Terms of rr: Using the surface area constraint: πr2+2πrh=61\pi r^2 + 2\pi rh = 61 Solve for hh: h=61πr22πrh = \frac{61 - \pi r^2}{2\pi r}

  2. Substitute hh into the Volume Formula: Substitute hh in the volume formula V=πr2hV = \pi r^2 h: V=πr2(61πr22πr)V = \pi r^2 \left( \frac{61 - \pi r^2}{2\pi r} \right) Simplify: V=r(61πr2)2V = \frac{r(61 - \pi r^2)}{2} This is the volume equation in terms of rr.

  3. Maximize the Volume: Take the derivative of VV with respect to rr and set it to zero to find the critical points: dVdr=6123πr22=0\frac{dV}{dr} = \frac{61}{2} - \frac{3\pi r^2}{2} = 0 Solve for rr: 3πr22=612\frac{3\pi r^2}{2} = \frac{61}{2} r2=613πr^2 = \frac{61}{3\pi} r=613πr = \sqrt{\frac{61}{3\pi}}

  4. Find hh using rr: Substitute rr back into the equation for hh: h=61π(613π)2π613πh = \frac{61 - \pi \left( \frac{61}{3\pi} \right)}{2\pi \sqrt{\frac{61}{3\pi}}} Simplifying this will give the height hh.

Let me calculate hh numerically to provide the exact height rounded to the nearest tenth.It seems like I can’t do more advanced data analysis right now. Please try again later.

However, I can guide you on how to compute the height step-by-step:

  1. Find the radius rr:

    • Use the formula r=613πr = \sqrt{\frac{61}{3\pi}}.
  2. Substitute rr into hh:

    • Use h=61πr22πrh = \frac{61 - \pi r^2}{2\pi r}.
  3. Evaluate and round hh:

    • Calculate hh and round it to the nearest tenth.

If you want to proceed with manual calculations or upload a new image for further help, let me know!

Related Questions

  1. How can we verify that the found height gives the maximum volume?
  2. What would the volume of the cylinder be using this height?
  3. How does the ratio between height and radius affect the maximum volume?
  4. Can this problem be solved using optimization techniques like Lagrange multipliers?
  5. What are the practical applications of this type of problem in real-world scenarios?

Tip: When solving optimization problems, always check the second derivative to confirm whether it is a maximum or minimum.

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Math Problem Analysis

Mathematical Concepts

Optimization
Geometry
Differentiation
Volume Maximization

Formulas

Surface Area (S) of open-top cylinder: S = πr² + 2πrh
Volume (V) of a cylinder: V = πr²h
Optimization through differentiation: dV/dr = 0

Theorems

Maximization using the first derivative test

Suitable Grade Level

Grades 10-12 (Pre-Calculus/Calculus level)