Abox of volume 60m3 with a squan botHom and no top IS constructd out of 2 diffennt materi als. The makerial for the botHom costs $40/m². The makri al for the sides costs $30/m? And the dimensions that minimalize total cost. (don't forget to Show that answer is a minimum) Leare answer exact or qire approximahon to 2 decimal places.
Unitary Method
The word “unitary” comes from the word “unit”, which means a single and complete entity. In this method, we find the value of a unit product from the given number of products, and then we solve for the other number of products.
Speed, Time, and Distance
Imagine you and 3 of your friends are planning to go to the playground at 6 in the evening. Your house is one mile away from the playground and one of your friends named Jim must start at 5 pm to reach the playground by walk. The other two friends are 3 miles away.
Profit and Loss
The amount earned or lost on the sale of one or more items is referred to as the profit or loss on that item.
Units and Measurements
Measurements and comparisons are the foundation of science and engineering. We, therefore, need rules that tell us how things are measured and compared. For these measurements and comparisons, we perform certain experiments, and we will need the experiments to set up the devices.
![### Problem Statement
A box of volume \(60 \, \text{m}^3\) with a square bottom and no top is constructed out of 2 different materials. The material for the bottom costs \( \$40/\text{m}^2 \). The material for the sides costs \( \$30/\text{m}^2 \).
Find the dimensions that minimize total cost. (Don't forget to show that your answer is a minimum). Leave answer exact or give approximation to 2 decimal places.
### Explanation
- **Volume of the Box:** \( V = 60 \, \text{m}^3 \)
- **Cost per Unit Area for Bottom Material:** \( \$40/\text{m}^2 \)
- **Cost per Unit Area for Side Material:** \( \$30/\text{m}^2 \)
### Step-by-Step Solution
1. **Determine the Variables:**
- Let \( x \) be the length of one side of the square base.
- Let \( h \) be the height of the box.
2. **Establish the Volume Constraint:**
- Volume: \( x^2 h = 60 \Rightarrow h = \frac{60}{x^2} \)
3. **Calculate the Surface Area:**
- Bottom area: \( x^2 \)
- Side area: \( 4xh \)
4. **Express Total Cost:**
- Cost for bottom: \( 40x^2 \)
- Cost for sides: \( 30 \cdot 4xh = 120xh \)
- Substitute for \( h \): \( 120x \left( \frac{60}{x^2} \right) = \frac{7200}{x} \)
- Total cost: \( C(x) = 40x^2 + \frac{7200}{x} \)
5. **Find the Minimum Cost:**
- Derive the cost function with respect to \( x \): \( C'(x) = 80x - \frac{7200}{x^2} \)
- Set the derivative to zero to find critical points: \( 80x - \frac{7200}{x^2} = 0 \Rightarrow 80x^3 = 7200 \Rightarrow x^3 = 90 \Rightarrow x = \sqrt](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F658f1c9e-9774-4e58-a527-3d55d09680d2%2Fc6614d4b-5198-4777-b931-d45e4aebcb44%2Fjp3gjcc_reoriented.jpeg&w=3840&q=75)
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