问题


There is a single choice question about college mathematics. Answer the question by replying A, B, C or D.
Question: There are 25 suitcases, 5 of which are damaged. Three suitcases are selected at random. What is the probability that exactly 2 are damaged?
A. 2/69
B. 1/30
C. 2/23
D. 12/125
Answer:

答案

模型 模型答案 正确答案
金声玉亮2.0

To find the probability that exactly 2 out of 3 selected suitcases are damaged, we can use the concept of combinations and the formula for probability.

First, let's find the total number of ways to select 3 suitcases out of 25:

Total combinations = C(25, 3) = 25! / (3! * (25-3)!) = 25! / (3! * 22!) = (25 * 24 * 23) / (3 * 2 * 1) = 125 * 24 * 23 / 6 = 2,300

Next, let's find the number of ways to select exactly 2 damaged suitcases out of 5 and 1 undamaged suitcase out of 20:

Combinations of 2 damaged suitcases = C(5, 2) = 5! / (2! * (5-2)!) = 5! / (2! * 3!) = (5 * 4) / (2 * 1) = 10

Combinations of 1 undamaged suitcase = C(20, 1) = 20! / (1! * (20-1)!) = 20

Now, we multiply the combinations of 2 damaged suitcases and 1 undamaged suitcase to get the total number of favorable outcomes:

Favorable outcomes = Combinations of 2 damaged suitcases * Combinations of 1 undamaged suitcase = 10 * 20 = 200

Finally, we can find the probability by dividing the number of favorable outcomes by the total number of combinations:

Probability = Favorable outcomes / Total combinations = 200 / 2,300

To simplify the fraction, we can divide both the numerator and the denominator by their greatest common divisor, which is 100:

Probability = (200 / 100) / (2,300 / 100) = 2 / 23

So, the probability that exactly 2 out of 3 selected suitcases are damaged is 2/23.

The correct answer is C.
C
deepseekr1

The problem involves calculating the probability of selecting exactly 2 damaged suitcases out of 3 chosen from 25 total (5 damaged, 20 undamaged).

1. **Total Combinations**: The number of ways to choose 3 suitcases from 25 is \( \binom{25}{3} \):
\[
\binom{25}{3} = \frac{25 \times 24 \times 23}{3 \times 2 \times 1} = 2300.
\]

2. **Favorable Combinations**: To have exactly 2 damaged and 1 undamaged suitcase:
- Choose 2 damaged from 5: \( \binom{5}{2} = \frac{5 \times 4}{2 \times 1} = 10 \).
- Choose 1 undamaged from 20: \( \binom{20}{1} = 20 \).
- Total favorable combinations: \( 10 \times 20 = 200 \).

3. **Probability**: Divide favorable by total combinations:
\[
\frac{200}{2300} = \frac{2}{23}.
\]

4. **Verification**: Using probability multiplication for specific orders (e.g., D-D-ND) and accounting for \( \binom{3}{2} = 3 \) arrangements:
\[
3 \times \left( \frac{5}{25} \times \frac{4}{24} \times \frac{20}{23} \right) = 3 \times \frac{2}{69} = \frac{6}{69} = \frac{2}{23}.
\]

Both methods confirm the answer is **C. 2/23**.

Answer: C
C
gpto1 C C
GPT-4o To determine the probability that exactly 2 out of the 3 selected suitcases are damaged, we can use combinations and the concept of probability.

First, we calculate the total number of ways to select 3 suitcases out of 25:
\[ \binom{25}{3} = \frac{25!}{3!(25-3)!} = \frac{25 \times 24 \times 23}{3 \times 2 \times 1} = 2300 \]

Next, we calculate the number of ways to select exactly 2 damaged suitcases out of the 5 damaged ones:
\[ \binom{5}{2} = \frac{5!}{2!(5-2)!} = \frac{5 \times 4}{2 \times 1} = 10 \]

We also need to select the remaining 1 suitcase from the 20 undamaged suitcases:
\[ \binom{20}{1} = \frac{20!}{1!(20-1)!} = 20 \]

Now, we multiply the number of ways to select the damaged suitcases by the number of ways to select the undamaged suitcase:
\[ 10 \times 20 = 200 \]

The probability is then the ratio of the favorable outcomes to the total outcomes:
\[ \frac{200}{2300} = \frac{2}{23} \]

Therefore, the probability that exactly 2 out of the 3 selected suitcases are damaged is:
\[ \boxed{\text{C}} \]

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

A
C
llama3.1-405B-Instruct

To find the probability that exactly 2 out of 3 selected suitcases are damaged, we can use the concept of combinations and the formula for probability.

First, let's find the total number of ways to select 3 suitcases out of 25:

Total combinations = C(25, 3) = 25! / (3! * (25-3)!) = 25! / (3! * 22!) = (25 * 24 * 23) / (3 * 2 * 1) = 125 * 24 * 23 / 6 = 2,300

Next, let's find the number of ways to select exactly 2 damaged suitcases out of 5 and 1 undamaged suitcase out of 20:

Combinations of 2 damaged suitcases = C(5, 2) = 5! / (2! * (5-2)!) = 5! / (2! * 3!) = (5 * 4) / (2 * 1) = 10

Combinations of 1 undamaged suitcase = C(20, 1) = 20! / (1! * (20-1)!) = 20

Now, we multiply the combinations of damaged and undamaged suitcases to get the total number of favorable outcomes:

Favorable outcomes = Combinations of 2 damaged suitcases * Combinations of 1 undamaged suitcase = 10 * 20 = 200

Finally, we can calculate the probability:

Probability = Favorable outcomes / Total combinations = 200 / 2,300

To simplify the fraction, we can divide both numerator and denominator by their greatest common divisor, which is 100:

Probability = (200 / 100) / (2,300 / 100) = 2 / 23

So, the probability that exactly 2 out of 3 selected suitcases are damaged is 2/23.

The correct answer is C.
C
DeepSeek-Coder-V2 C. 2/23 C
Qwen2-72B-Instruct The probability that exactly 2 out of 3 selected suitcases are damaged can be calculated using combinations. There are 5 damaged suitcases and 20 undamaged suitcases.

The number of ways to choose 2 damaged suitcases out of 5 is given by the combination formula \(C(n, k) = \frac{n!}{k!(n-k)!}\), where \(n\) is the total number of items, \(k\) is the number of items to choose, and \(!\) denotes factorial.

So, the number of ways to choose 2 damaged suitcases out of 5 is \(C(5, 2) = \frac{5!}{2!(5-2)!} = 10\).

The number of ways to choose 1 undamaged suitcase out of 20 is \(C(20, 1) = \frac{20!}{1!(20-1)!} = 20\).

The total number of ways to choose 3 suitcases out of 25 is \(C(25, 3) = \frac{25!}{3!(25-3)!} = 2300\).

Therefore, the probability that exactly 2 out of the 3 selected suitcases are damaged is \(\frac{10 \times 20}{2300} = \frac{200}{2300} = \frac{20}{230} = \frac{2}{23}\).

Answer: C. 2/23
C
baichuan4 D C
doubao D. 12/125

The total number of ways to choose 3 suitcases out of 25 is C(25,3). The number of ways to choose 2 damaged suitcases out of 5 is C(5,2), and the number of ways to choose 1 undamaged suitcase out of 20 is C(20,1). The probability of exactly 2 damaged suitcases is [C(5,2) * C(20,1)] / C(25,3) = 12/125.
C
minimax To solve this problem, we can use combinations to calculate the probability of selecting exactly 2 damaged suitcases out of 3 selected.

First, we calculate the number of ways to choose 2 damaged suitcases from the 5 available. This is given by the combination formula:

C(5, 2) = 5! / (2! * (5 - 2)!) = (5 * 4) / (2 * 1) = 10 ways.

Next, we calculate the number of ways to choose 1 undamaged suitcase from the 20 available (since there are 25 - 5 = 20 undamaged suitcases). This is given by:

C(20, 1) = 20! / (1! * (20 - 1)!) = 20 ways.

Now, we multiply these two results to find the total number of ways to choose exactly 2 damaged suitcases and 1 undamaged suitcase:

10 ways (damaged) * 20 ways (undamaged) = 200 ways.

Finally, we calculate the total number of ways to choose any 3 suitcases from the 25:

C(25, 3) = 25! / (3! * (25 - 3)!) = (25 * 24 * 23) / (3 * 2 * 1) = 2300 ways.

The probability of selecting exactly 2 damaged suitcases is the number of favorable outcomes divided by the total number of outcomes:

Probability = 200 / 2300 = 20 / 230 = 2 / 23.

So the correct answer is:

C. 2/23
C
kimi To solve this problem, we need to calculate the probability of selecting exactly 2 damaged suitcases out of 5 and 1 undamaged suitcase out of 20 (since there are 25 suitcases in total and 5 are damaged).

First, let's calculate the total number of ways to select 3 suitcases out of 25. This is a combination problem, which can be solved using the formula for combinations:

\[ C(n, k) = \frac{n!}{k!(n-k)!} \]

where \( n \) is the total number of items, \( k \) is the number of items to choose, and \( ! \) denotes factorial.

The total number of ways to choose 3 suitcases from 25 is:

\[ C(25, 3) = \frac{25!}{3!(25-3)!} = \frac{25!}{3! \cdot 22!} \]

Now, let's calculate the number of ways to choose exactly 2 damaged suitcases from 5 and 1 undamaged suitcase from 20:

\[ C(5, 2) \times C(20, 1) = \frac{5!}{2!(5-2)!} \times \frac{20!}{1!(20-1)!} \]

\[ = \frac{5!}{2! \cdot 3!} \times \frac{20!}{1! \cdot 19!} \]

\[ = \frac{5 \times 4}{2 \times 1} \times 20 \]

\[ = 10 \times 20 \]

\[ = 200 \]

Now, we calculate the probability by dividing the number of favorable outcomes by the total number of outcomes:

\[ P(\text{exactly 2 damaged}) = \frac{C(5, 2) \times C(20, 1)}{C(25, 3)} \]

\[ = \frac{200}{\frac{25 \times 24 \times 23}{3 \times 2 \times 1}} \]

\[ = \frac{200}{2300} \]

\[ = \frac{4}{23} \]

However, none of the options match this result. Let's re-evaluate the calculation:

\[ C(25, 3) = \frac{25 \times 24 \times 23}{3 \times 2 \times 1} = 2300 \]

\[ C(5, 2) \times C(20, 1) = 10 \times 20 = 200 \]

\[ P(\text{exactly 2 damaged}) = \frac{200}{2300} = \frac{200}{2300} \times \frac{100}{100} = \frac{20000}{23000} = \frac{100}{115} \]

\[ = \frac{20}{23} \]

This result is still not matching any of the options, so there must be a mistake in the calculation. Let's try again:

\[ C(25, 3) = \frac{25 \times 24 \times 23}{3 \times 2 \times 1} = 2300 \]

\[ C(5, 2) \times C(20, 1) = \frac{5 \times 4}{2 \times 1} \times 20 = 200 \]

\[ P(\text{exactly 2 damaged}) = \frac{200}{2300} \]

\[ = \frac{200}{2300} \times \frac{100}{100} = \frac{20000}{23000} \]

\[ = \frac{100}{115} \]

\[ = \frac{20}{23} \]

This is incorrect. Let's correct the calculation:

\[ C(25, 3) = \frac{25 \times 24 \times 23}{3 \times 2 \times 1} = 2300 \]

\[ C(5, 2) \times C(20, 1) = \frac{5 \times 4}{2 \times 1} \times 20 = 200 \]

\[ P(\text{exactly 2 damaged}) = \frac{200}{2300} = \frac{20}{230} = \frac{2}{23} \]

So the correct probability is \( \frac{2}{23} \), which corresponds to option C.

Answer: C.
C
wenxinyiyan C

Explanation:

To solve this problem, we can use the combination formula to calculate the probabilities.

The combination formula is defined as:
C(n, k) = n! / (k!(n-k)!)

where n is the total number of items, k is the number of items we want to select, and ! represents the factorial operation.

Let's define the following events:
D: selecting a damaged suitcase
N: selecting an undamaged suitcase

We want to find the probability of selecting exactly 2 damaged suitcases out of 3 selected suitcases. This can be represented as:
P(D, D, N) or P(D, N, D) or P(N, D, D)

Since the order of selection doesn't matter, we can combine these probabilities into one formula:
P(exactly 2 damaged) = (C(5, 2) * C(20, 1)) / C(25, 3)

where:
C(5, 2) is the number of ways to select 2 damaged suitcases from 5 damaged suitcases.
C(20, 1) is the number of ways to select 1 undamaged suitcase from 20 undamaged suitcases.
C(25, 3) is the total number of ways to select 3 suitcases from 25 suitcases.

Calculating these combinations:
C(5, 2) = 5! / (2! * (5-2)!) = 10
C(20, 1) = 20! / (1! * (20-1)!) = 20
C(25, 3) = 25! / (3! * (25-3)!) = 2300

Plugging these values into our probability formula:
P(exactly 2 damaged) = (10 * 20) / 2300 = 200 / 2300 = 2 / 23

So the answer is C: 2/23.
C
zhipu To solve this problem, we need to calculate the probability of selecting exactly 2 damaged suitcases out of the 3 selected from the 25 suitcases, where 5 are damaged and 20 are not damaged.

First, let's define the events:
- Total number of suitcases: \( n = 25 \)
- Number of damaged suitcases: \( d = 5 \)
- Number of non-damaged suitcases: \( n - d = 20 \)
- Number of suitcases selected: \( k = 3 \)

We need to find the probability of selecting exactly 2 damaged suitcases and 1 non-damaged suitcase.

The number of ways to choose 2 damaged suitcases from 5 is given by the combination formula \( \binom{d}{2} \):
\[ \binom{5}{2} = \frac{5!}{2!(5-2)!} = \frac{5 \times 4}{2 \times 1} = 10 \]

The number of ways to choose 1 non-damaged suitcase from 20 is given by the combination formula \( \binom{20}{1} \):
\[ \binom{20}{1} = 20 \]

So, the number of favorable ways to choose exactly 2 damaged and 1 non-damaged suitcase is:
\[ \binom{5}{2} \times \binom{20}{1} = 10 \times 20 = 200 \]

Next, we need to find the total number of ways to choose 3 suitcases from 25, which is given by the combination formula \( \binom{25}{3} \):
\[ \binom{25}{3} = \frac{25!}{3!(25-3)!} = \frac{25 \times 24 \times 23}{3 \times 2 \times 1} = 2300 \]

Therefore, the probability of selecting exactly 2 damaged suitcases out of the 3 selected is:
\[ P(\text{exactly 2 damaged}) = \frac{\text{Number of favorable ways}}{\text{Total number of ways}} = \frac{200}{2300} = \frac{2}{23} \]

So, the correct answer is:
C. 2/23
C
gpto1 C C
deepseekv3 To solve this problem, we can use the concept of **combinations** in probability.

**Given:**
- Total suitcases: 25
- Damaged suitcases: 5
- Non-damaged suitcases: 20
- Suitcases selected: 3

**Goal:**
Find the probability that exactly 2 of the selected suitcases are damaged.

---

### Step 1: Total number of ways to select 3 suitcases
The total number of ways to select 3 suitcases out of 25 is given by the combination formula:

\[
\text{Total ways} = \binom{25}{3} = \frac{25!}{3!(25-3)!} = \frac{25 \times 24 \times 23}{3 \times 2 \times 1} = 2300
\]

---

### Step 2: Number of favorable outcomes (exactly 2 damaged)
To have exactly 2 damaged suitcases, we need to:
1. Choose 2 damaged suitcases out of 5.
2. Choose 1 non-damaged suitcase out of 20.

The number of ways to do this is:

\[
\text{Favorable ways} = \binom{5}{2} \times \binom{20}{1} = \frac{5!}{2!(5-2)!} \times 20 = \frac{5 \times 4}{2 \times 1} \times 20 = 10 \times 20 = 200
\]

---

### Step 3: Calculate the probability
The probability is the ratio of favorable outcomes to total outcomes:

\[
\text{Probability} = \frac{\text{Favorable ways}}{\text{Total ways}} = \frac{200}{2300} = \frac{2}{23}
\]

---

### Final Answer:
**C. 2/23**
C