问题


There is a single choice question about high school mathematics. Answer the question by replying A, B, C or D.
Question: The amount of paint that David needs to cover a cube is directly proportional to the surface area. If David can completely cover a cube of side length 2 feet with exactly 16 quarts of paint, how big a cube (in terms of edge length in feet) can David cover with 169 quarts of paint?
A. \frac{13}{4}
B. 8
C. \frac{13}{2}
D. 13
Answer:

答案

模型 模型答案 正确答案
金声玉亮2.0

C. If the amount of paint David needs is directly proportional to the surface area of the cube, then p = k × s , where p is the amount of paint, s is the surface area of the cube, and k is a constant. The surface area of a cube is 6 e ^{2}, where e is the length of the edge of the cube. Therefore, p = k × 6 e ^{2}. You know that e = 2 when p = 16, so 16 = k × 6 × 2^{2} = 24 k . Therefore, k = $\frac{2}{3}$ . Now, when p = 169, you have 169 = $\frac{2}{3}$ × 6 e ^{2}, so 169 = 4 e ^{2}. Thus, e = $\frac{13}{2}$ , which is (C).
The best answer is C.
C
deepseekr1

The amount of paint required is directly proportional to the surface area of the cube. For a cube with side length \( s \), the surface area is \( 6s^2 \). Given that 16 quarts cover a 2-foot cube, its surface area is \( 6(2)^2 = 24 \, \text{ft}^2 \). The proportionality constant \( k \) is calculated as \( k = \frac{16}{24} = \frac{2}{3} \) quarts per square foot.

For 169 quarts, the surface area covered is \( \frac{169}{k} = \frac{169}{2/3} = 253.5 \, \text{ft}^2 \). Setting \( 6s^2 = 253.5 \), solving gives \( s^2 = \frac{253.5}{6} = 42.25 \), so \( s = \sqrt{42.25} = 6.5 = \frac{13}{2} \).

**Answer: C**
C
gpto1 C C
GPT-4o To solve this problem, we need to find the relationship between the surface area of the cube and the amount of paint needed to cover it.

First, let's determine the surface area of a cube with a side length of 2 feet. The surface area \( A \) of a cube is given by the formula:
\[ A = 6s^2 \]
where \( s \) is the side length of the cube.

For \( s = 2 \) feet:
\[ A = 6 \times (2^2) = 6 \times 4 = 24 \text{ square feet} \]

We know that 16 quarts of paint are needed to cover 24 square feet. Given that the amount of paint needed is directly proportional to the surface area, we can set up the following proportion to find the amount of paint needed for any surface area \( A \):
\[ \frac{16 \text{ quarts}}{24 \text{ square feet}} = \frac{P \text{ quarts}}{A \text{ square feet}} \]

We need to find the surface area \( A \) that corresponds to 169 quarts of paint:
\[ \frac{16}{24} = \frac{169}{A} \]

Solving for \( A \):
\[ A = \frac{169 \times 24}{16} = 253.5 \text{ square feet} \]

Next, we need to find the side length \( s \) of the cube that has a surface area of 253.5 square feet. Using the surface area formula for a cube:
\[ 6s^2 = 253.5 \]

Solving for \( s \):
\[ s^2 = \frac{253.5}{6} = 42.25 \]
\[ s = \sqrt{42.25} = 6.5 \text{ feet} \]

Therefore, David can cover a cube with an edge length of 6.5 feet with 169 quarts of paint.

Given the options:
A. \(\frac{13}{4}\)
B. 8
C. \(\frac{13}{2}\)
D. 13

The correct answer is:
\[ 6.5 = \frac{13}{2} \]

Answer: C
C
llama3.1-70B-Instruct

A
C
llama3.1-405B-Instruct

C
The best answer is C.
C
DeepSeek-Coder-V2 C. \frac{13}{2} C
Qwen2-72B-Instruct The amount of paint needed to cover a cube is directly proportional to its surface area. The surface area of a cube is given by \(6s^2\), where \(s\) is the side length.

Given that 16 quarts of paint cover a cube of side length 2 feet, we can find the constant of proportionality, \(k\), such that \(16 = k \cdot 6 \cdot 2^2\). Simplifying, we get \(16 = 24k\), so \(k = \frac{2}{3}\).

Now, we are given 169 quarts of paint and want to find the side length (\(s\)) of the cube that can be covered. We use the proportionality relationship, so \(169 = k \cdot 6s^2\). Substituting for \(k\), we get \(169 = \frac{2}{3} \cdot 6s^2\), which simplifies to \(169 = 4s^2\). Solving for \(s^2\), we get \(s^2 = \frac{169}{4}\), so \(s = \sqrt{\frac{169}{4}} = \frac{13}{2}\).

Therefore, the answer is C. \(\frac{13}{2}\).
C
baichuan4 The surface area of a cube with side length 2 feet is 6*(2^2) = 24 square feet.

If 16 quarts of paint covers 24 square feet, then 169 quarts of paint will cover (169/16)*24 = 253.5 square feet.

The surface area of a cube with side length x is 6*x^2. Setting this equal to 253.5 gives us 6*x^2 = 253.5, so x^2 = 42.25.

Taking the square root of both sides gives us x = √42.25 = 6.5.

Therefore, the correct answer is A. \frac{13}{2}.
C
doubao D

The surface area of a cube with side length s is 6s^2. For the first cube with side length 2 feet, the surface area is 6×2^2 = 6×4 = 24 square feet and it requires 16 quarts of paint. So the ratio of paint to surface area is 16/24 = 2/3. If we have 169 quarts of paint, then the surface area is 169×(3/2) = 253.5 square feet. Let the side length of the new cube be x. Then 6x^2 = 253.5, x^2 = 253.5/6 = 42.25, x = 6.5 = 13/2 feet.
C
minimax Let's denote the side length of the first cube as \( s \) and the side length of the second cube as \( S \). We know that David can cover a cube of side length \( s = 2 \) feet with 16 quarts of paint.

The surface area of a cube is given by \( 6 \times \text{side length}^2 \). So, the surface area of the first cube is \( 6 \times 2^2 = 6 \times 4 = 24 \) square feet.

Since the amount of paint needed is directly proportional to the surface area, we can set up a proportion to find the side length \( S \) of the cube that David can cover with 169 quarts of paint.

Let \( A \) be the surface area of the second cube. We have:

\[
\frac{16 \text{ quarts}}{24 \text{ square feet}} = \frac{169 \text{ quarts}}{A}
\]

Solving for \( A \):

\[
A = \frac{169 \times 24}{16} = \frac{169 \times 3}{2} = \frac{507}{2} = 253.5 \text{ square feet}
\]

Now, we know that \( A \) is the surface area of the second cube, so:

\[
A = 6 \times S^2 = 253.5
\]

Solving for \( S \):

\[
S^2 = \frac{253.5}{6} = 42.25
\]

\[
S = \sqrt{42.25} = 6.5
\]

None of the options match \( S = 6.5 \) feet, so it seems there might be a mistake in the options provided. However, if we consider the possibility of a typo or error in the options, the closest one to the correct answer would be option C, \( \frac{13}{2} \), which is equal to 6.5. Therefore, the answer is:

C. \( \frac{13}{2} \)
C
kimi Let's solve the problem step by step.

1. **Understanding the relationship**: The amount of paint needed is directly proportional to the surface area of the cube.

2. **Surface area of a cube**: The surface area \( A \) of a cube with side length \( s \) is given by \( A = 6s^2 \).

3. **Given information**: David can cover a cube with side length 2 feet with 16 quarts of paint. So, for the cube with side length \( s = 2 \) feet, the surface area is \( A = 6 \times 2^2 = 24 \) square feet. Since the amount of paint is proportional to the surface area, the ratio of paint to surface area is \( \frac{16 \text{ quarts}}{24 \text{ square feet}} = \frac{2}{3} \text{ quarts per square foot} \).

4. **Paint needed for a larger cube**: David has 169 quarts of paint. Let \( s' \) be the side length of the larger cube. The surface area of this larger cube is \( A' = 6s'^2 \). The amount of paint needed for this larger cube is \( \frac{2}{3} \times A' \).

5. **Setting up the equation**: Since the amount of paint is 169 quarts, we have:
\[
\frac{2}{3} \times 6s'^2 = 169
\]
Simplifying, we get:
\[
4s'^2 = 169
\]
\[
s'^2 = \frac{169}{4}
\]
\[
s' = \sqrt{\frac{169}{4}} = \frac{13}{2}
\]

6. **Answer**: The side length of the larger cube that David can cover with 169 quarts of paint is \( \frac{13}{2} \) feet.

So, the correct answer is:
C. \( \frac{13}{2} \)
C
wenxinyiyan C

Explanation:

1. **Find the Surface Area of the Given Cube**:


* A cube has 6 faces, each with an area of $s^2$, where $s$ is the side length.
* For the given cube with a side length of 2 feet, the surface area is $6 \times 2^2 = 24$ square feet.
2. **Determine the Proportionality Constant**:


* Since the amount of paint is directly proportional to the surface area, we can write: $\text{Paint} = k \times \text{Surface Area}$
* Using the given information, $16 = k \times 24$
* Solving for $k$, we get $k = \frac{2}{3}$
3. **Find the Surface Area for 169 Quarts of Paint**:


* Using the proportionality constant, we can find the surface area covered by 169 quarts of paint: $169 = \frac{2}{3} \times \text{Surface Area}$
* Solving for the surface area, we get $\text{Surface Area} = \frac{169 \times 3}{2} = 253.5$ square feet.
4. **Determine the Side Length of the New Cube**:


* Since the surface area of a cube is $6s^2$, we can solve for $s$ using the new surface area: $6s^2 = 253.5$
* Solving for $s$, we get $s = \sqrt{\frac{253.5}{6}} = \frac{13}{2}$ feet.
C
zhipu To determine the edge length of the cube that David can cover with 169 quarts of paint, we need to understand the relationship between the amount of paint and the surface area of the cube.

First, let's find the surface area of the original cube with a side length of 2 feet:
\[ \text{Surface area of a cube} = 6 \times (\text{side length})^2 \]
For a cube with a side length of 2 feet:
\[ \text{Surface area} = 6 \times (2)^2 = 6 \times 4 = 24 \text{ square feet} \]

David uses 16 quarts of paint to cover this 24 square feet. Therefore, the amount of paint needed per square foot is:
\[ \frac{16 \text{ quarts}}{24 \text{ square feet}} = \frac{2}{3} \text{ quarts per square foot} \]

Next, we need to find the surface area that can be covered with 169 quarts of paint:
\[ \text{Surface area} = \frac{169 \text{ quarts}}{\frac{2}{3} \text{ quarts per square foot}} = 169 \times \frac{3}{2} = 253.5 \text{ square feet} \]

Now, we need to find the side length of a cube that has this surface area:
\[ 6 \times (\text{side length})^2 = 253.5 \]
\[ (\text{side length})^2 = \frac{253.5}{6} = 42.25 \]
\[ \text{side length} = \sqrt{42.25} = 6.5 \text{ feet} \]

Therefore, the edge length of the cube that David can cover with 169 quarts of paint is 6.5 feet, which corresponds to:
\[ \frac{13}{2} \text{ feet} \]

So, the correct answer is:
C. \(\frac{13}{2}\)
C
gpto1 C C
deepseekv3 To solve this problem, we need to understand the relationship between the amount of paint and the surface area of the cube.

1. **Calculate the surface area of the initial cube:**
The surface area \( S \) of a cube with side length \( s \) is given by:
\[
S = 6s^2
\]
For a cube with side length 2 feet:
\[
S = 6 \times 2^2 = 6 \times 4 = 24 \text{ square feet}
\]

2. **Determine the proportionality constant:**
The amount of paint \( P \) is directly proportional to the surface area \( S \). Therefore:
\[
P = kS
\]
Given that 16 quarts of paint cover 24 square feet:
\[
16 = k \times 24 \implies k = \frac{16}{24} = \frac{2}{3}
\]

3. **Find the surface area that 169 quarts can cover:**
Using the proportionality constant \( k \):
\[
169 = \frac{2}{3} \times S \implies S = \frac{169 \times 3}{2} = 253.5 \text{ square feet}
\]

4. **Calculate the side length of the new cube:**
Using the surface area formula:
\[
6s^2 = 253.5 \implies s^2 = \frac{253.5}{6} = 42.25 \implies s = \sqrt{42.25} = 6.5 \text{ feet}
\]
Converting 6.5 feet to a fraction:
\[
6.5 = \frac{13}{2} \text{ feet}
\]

Therefore, the correct answer is:

**C. \(\frac{13}{2}\)**
C