Math Problem Statement

Determine Divide 24 into three parts such that the continued product of the first, square of the second, and cube of the third is maximum.

Solution

This problem asks to divide 24 into three parts xx, yy, and zz such that the continued product xy2z3x \cdot y^2 \cdot z^3 is maximized.

Let’s solve this step by step:

Step 1: Define the constraints.

  1. x+y+z=24x + y + z = 24 (since the sum of the three parts is 24).
  2. The function to maximize is P=xy2z3P = x \cdot y^2 \cdot z^3.

Step 2: Solve using the method of Lagrange multipliers.

Introduce a Lagrange multiplier λ\lambda for the constraint x+y+z=24x + y + z = 24. Define: L(x,y,z,λ)=xy2z3λ(x+y+z24).L(x, y, z, \lambda) = x \cdot y^2 \cdot z^3 - \lambda (x + y + z - 24).

Step 3: Take partial derivatives.

Compute the partial derivatives of LL with respect to xx, yy, zz, and λ\lambda, and set them equal to zero:

  1. Lx=y2z3λ=0\frac{\partial L}{\partial x} = y^2 z^3 - \lambda = 0.
  2. Ly=2xyz3λ=0\frac{\partial L}{\partial y} = 2x y z^3 - \lambda = 0.
  3. Lz=3xy2z2λ=0\frac{\partial L}{\partial z} = 3x y^2 z^2 - \lambda = 0.
  4. Lλ=(x+y+z24)=0\frac{\partial L}{\partial \lambda} = -(x + y + z - 24) = 0.

Step 4: Simplify.

From the first three equations: λ=y2z3,λ=2xyz3,λ=3xy2z2.\lambda = y^2 z^3, \quad \lambda = 2x y z^3, \quad \lambda = 3x y^2 z^2. Equate y2z3=2xyz3y^2 z^3 = 2x y z^3, divide through by yz3y z^3 (assuming y,z0y, z \neq 0): y=2x.y = 2x. Equate y2z3=3xy2z2y^2 z^3 = 3x y^2 z^2, divide through by y2z2y^2 z^2 (assuming y,z0y, z \neq 0): z=3x.z = 3x.

Step 5: Substitute into the constraint.

Using y=2xy = 2x and z=3xz = 3x in x+y+z=24x + y + z = 24: x+2x+3x=24.x + 2x + 3x = 24. 6x=24    x=4.6x = 24 \implies x = 4. Then: y=2x=8,z=3x=12.y = 2x = 8, \quad z = 3x = 12.

Step 6: Verify the solution.

The three parts are x=4x = 4, y=8y = 8, z=12z = 12. The product P=xy2z3P = x \cdot y^2 \cdot z^3 becomes: P=482123=4641728=442,368.P = 4 \cdot 8^2 \cdot 12^3 = 4 \cdot 64 \cdot 1728 = 442,368.

Thus, the maximum product occurs when x=4x = 4, y=8y = 8, and z=12z = 12.


Would you like me to provide a detailed explanation of any step?

Related Questions:

  1. How does the method of Lagrange multipliers work in optimization problems?
  2. Can you apply this method to divide a different sum (e.g., 36) into three parts for maximum product?
  3. What happens if x,y,zx, y, z are constrained to integers?
  4. Can this be solved using numerical methods instead of calculus?
  5. How do higher powers (e.g., x2,y3,z4x^2, y^3, z^4) affect the solution?

Tip:

When solving maximization problems with constraints, always check the boundary conditions (e.g., if one of x,y,zx, y, z equals zero).

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Math Problem Analysis

Mathematical Concepts

Optimization
Algebra
Lagrange Multipliers

Formulas

P = x * y^2 * z^3
Constraint: x + y + z = 24
L(x, y, z, λ) = x * y^2 * z^3 - λ * (x + y + z - 24)

Theorems

Lagrange Multiplier Method

Suitable Grade Level

Grades 11-12 or College Level