Math Problem Statement

Imagine George Washington has preferences for wooden teeth (T) and powdered wigs (W) that can be represented by the utility function: U(T, W) = T^0.6W^0.2. Mr. Washington does not know his budget or the prices of wooden teeth and powdered wigs. Please solve the following questions related to optimization, Lagrangian formulation, and first-order conditions. Then, solve for Mr. Washington's optimal bundle of wooden teeth and powdered wigs when his budget is $360, the price of each wooden tooth is $10, and the price of each powdered wig is $30.

Solution

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Question Overview:

  1. Utility Function: U(T,W)=T0.6W0.2U(T, W) = T^{0.6} W^{0.2}
    • TT represents the number of wooden teeth.
    • WW represents the number of powdered wigs.
    • PTP_T is the price of wooden teeth, and PWP_W is the price of powdered wigs.
    • MM is Mr. Washington’s budget.

a) Write out the optimization problem (utility and budget constraint):

  • Utility: U(T,W)=T0.6W0.2U(T, W) = T^{0.6} W^{0.2}
  • Budget constraint: PTT+PWW=MP_T T + P_W W = M

The goal is to maximize Mr. Washington’s utility given the budget constraint.

b) Lagrangian Function:

We set up the Lagrangian L(T,W,λ)\mathcal{L}(T, W, \lambda) to incorporate the utility maximization and the budget constraint.

L(T,W,λ)=T0.6W0.2+λ(MPTTPWW)\mathcal{L}(T, W, \lambda) = T^{0.6} W^{0.2} + \lambda (M - P_T T - P_W W)

c) First-order conditions (FOCs):

To solve this optimization, we take the first-order partial derivatives of the Lagrangian with respect to TT, WW, and λ\lambda and set them equal to 0.

  1. LT=0.6T0.4W0.2λPT=0\frac{\partial \mathcal{L}}{\partial T} = 0.6T^{-0.4}W^{0.2} - \lambda P_T = 0
  2. LW=0.2T0.6W0.8λPW=0\frac{\partial \mathcal{L}}{\partial W} = 0.2T^{0.6}W^{-0.8} - \lambda P_W = 0
  3. Lλ=MPTTPWW=0\frac{\partial \mathcal{L}}{\partial \lambda} = M - P_T T - P_W W = 0

These are the first-order conditions for TT, WW, and λ\lambda.


d) Solving for the optimal bundle (given specific values):

  • Budget M=360M = 360
  • Price of wooden teeth PT=10P_T = 10
  • Price of powdered wigs PW=30P_W = 30

To find the optimal TT^* and WW^*, we'll use the FOCs.

  1. From the first two FOCs, we can express the ratio of marginal utilities to prices:

0.6T0.4W0.20.2T0.6W0.8=PTPW\frac{0.6T^{-0.4}W^{0.2}}{0.2T^{0.6}W^{-0.8}} = \frac{P_T}{P_W} Simplifying this expression: 3WT=PTPW=1030=13\frac{3W}{T} = \frac{P_T}{P_W} = \frac{10}{30} = \frac{1}{3}

Thus, W=T9W = \frac{T}{9}.

  1. Substituting W=T9W = \frac{T}{9} into the budget constraint:

PTT+PWW=MP_T T + P_W W = M 10T+30(T9)=36010T + 30\left(\frac{T}{9}\right) = 360 10T+30T9=36010T + \frac{30T}{9} = 360 Multiplying the entire equation by 9 to eliminate the fraction: 90T+30T=360×990T + 30T = 360 \times 9 120T=3240120T = 3240 T=3240120=27T^* = \frac{3240}{120} = 27

  1. Now, substitute T=27T^* = 27 back into W=T9W = \frac{T}{9}:

W=279=3W^* = \frac{27}{9} = 3

Thus, Mr. Washington's optimal bundle is T=27T^* = 27 wooden teeth and W=3W^* = 3 powdered wigs.


g) Spending on wooden teeth and powdered wigs:

  • Spending on wooden teeth: PTT=10×27=270P_T T^* = 10 \times 27 = 270
  • Spending on powdered wigs: PWW=30×3=90P_W W^* = 30 \times 3 = 90

Total spending: 270+90=360270 + 90 = 360, which matches the budget.

  • Percentage spent on wooden teeth: 270360×100=75%\frac{270}{360} \times 100 = 75\%
  • Percentage spent on powdered wigs: 90360×100=25%\frac{90}{360} \times 100 = 25\%

Would you like any further explanation or more details? Here are some relative questions:

  1. How does the Lagrange multiplier λ\lambda relate to the optimization?
  2. Why is the ratio of marginal utilities to prices important in utility maximization?
  3. How would a change in prices PTP_T or PWP_W affect the optimal bundle?
  4. Could the same utility function apply if the prices were significantly different?
  5. What would happen if Mr. Washington had a larger budget?

Tip: Always check if your solution satisfies both the utility function and the budget constraint to ensure correctness.

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Math Problem Analysis

Mathematical Concepts

Optimization
Utility Maximization
Budget Constraints

Formulas

Utility function: U(T, W) = T^0.6 W^0.2
Budget constraint: P_T T + P_W W = M
Lagrangian function: L(T, W, λ) = T^0.6 W^0.2 + λ(M - P_T T - P_W W)
First-order conditions: dL/dT = 0.6T^(-0.4)W^0.2 - λP_T = 0, dL/dW = 0.2T^0.6W^(-0.8) - λP_W = 0

Theorems

Lagrange Multiplier
First-Order Conditions for Optimization

Suitable Grade Level

University-level Economics