Math Problem Statement

The sum of the first and twice the second is 100 and the product is a maximum.

Solution

This problem involves optimizing the product of two numbers under the constraint that their sum is related to another variable. Let's solve it step by step:


Step 1: Define the variables

Let the two numbers be xx (the first number) and yy (the second number).

From the problem:

  • Sum constraint: x+2y=100x + 2y = 100
  • Objective: Maximize the product P=xyP = xy.

Step 2: Express xx in terms of yy

From the constraint x+2y=100x + 2y = 100, solve for xx: x=1002yx = 100 - 2y


Step 3: Write the product in terms of yy

The product P=xyP = xy becomes: P=(1002y)yP = (100 - 2y)y Simplify: P=100y2y2P = 100y - 2y^2


Step 4: Maximize the product

To maximize PP, take its derivative with respect to yy and set it to zero: dPdy=1004y\frac{dP}{dy} = 100 - 4y Set dPdy=0\frac{dP}{dy} = 0: 1004y=0    y=25100 - 4y = 0 \implies y = 25


Step 5: Find xx and verify the maximum

Using x=1002yx = 100 - 2y, substitute y=25y = 25: x=1002(25)=50x = 100 - 2(25) = 50

The numbers are x=50x = 50 and y=25y = 25.


Step 6: Verify the maximum

The second derivative of PP is: d2Pdy2=4\frac{d^2P}{dy^2} = -4 Since d2Pdy2<0\frac{d^2P}{dy^2} < 0, the function PP has a maximum at y=25y = 25.


Final Answer:

The numbers are x=50x = 50 and y=25y = 25. The maximum product is: P=5025=1250P = 50 \cdot 25 = 1250


Would you like a detailed explanation of any step?

Here are 5 related questions to explore further:

  1. How do you determine whether a critical point is a maximum or minimum?
  2. What is the significance of the second derivative test in optimization problems?
  3. How would the solution change if the constraint was x+3y=100x + 3y = 100?
  4. Can you generalize this method for different constraints?
  5. How is this method applied in real-world problems, like economics or engineering?

Tip: When solving optimization problems, always verify that your solution satisfies the original constraint!

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Math Problem Analysis

Mathematical Concepts

Algebra
Optimization
Derivatives

Formulas

x + 2y = 100
P = xy
P = 100y - 2y^2

Theorems

First Derivative Test
Second Derivative Test

Suitable Grade Level

Grades 10-12