Calculating the Probability of Pulling Out a 3 First

Oct 13, 2025 by wbrum.org 80 views

Introduction

In this problem, we are presented with a stack of cards containing numbers from the set $\{1, 1, 2, 2, 3, 3, 3, 4\}$ . Hiro wants to pull out a 3 first and then a 2 without replacing them. We need to calculate the probability of this specific sequence of events.

Understanding the Problem

To solve this problem, we need to understand the concept of probability. Probability is a measure of the likelihood of an event occurring. In this case, we are interested in the probability of two events: pulling out a 3 first and then pulling out a 2.

Calculating the Probability of Pulling Out a 3 First

Let's start by calculating the probability of pulling out a 3 first. There are 8 cards in total, and 3 of them have the number 3 written on them. Therefore, the probability of pulling out a 3 first is:

P(\text{3 first}) = \frac{\text{Number of 3's}}{\text{Total number of cards}} = \frac{3}{8}

Calculating the Probability of Pulling Out a 2 Second

Now, let's calculate the probability of pulling out a 2 second. After pulling out a 3 first, there are 7 cards left, and 2 of them have the number 2 written on them. However, we need to take into account that the card with the number 3 is not replaced, so the total number of cards is still 7. Therefore, the probability of pulling out a 2 second is:

P(\text{2 second}) = \frac{\text{Number of 2's}}{\text{Total number of cards after pulling out a 3}} = \frac{2}{7}

Calculating the Overall Probability

To calculate the overall probability of pulling out a 3 first and then a 2, we need to multiply the probabilities of each event:

P(\text{3 first and then 2}) = P(\text{3 first}) \times P(\text{2 second}) = \frac{3}{8} \times \frac{2}{7} = \frac{6}{56} = \frac{3}{28}

Conclusion

In conclusion, the probability of Hiro pulling out a 3 first and then a 2 without replacing them is $\frac{3}{28}$ .

Final Answer

The final answer is $\boxed{\frac{3}{28}}$ .

Discussion

This problem requires a good understanding of probability and the concept of conditional probability. The key to solving this problem is to calculate the probability of each event separately and then multiply them together. This problem can be used to illustrate the concept of conditional probability and how it can be used to calculate the probability of a specific sequence of events.

Solutions to Related Problems

Some solutions to related problems include:

Calculating the probability of pulling out a specific card from a deck of cards: This can be done by calculating the probability of each card separately and then multiplying them together.
Calculating the probability of rolling a specific number on a die: This can be done by calculating the probability of each number separately and then multiplying them together.
Calculating the probability of drawing a specific card from a deck of cards: This can be done by calculating the probability of each card separately and then multiplying them together.

Conclusion

Q: What is the probability of pulling out a 3 first and then a 2 without replacing them?

A: The probability of pulling out a 3 first and then a 2 without replacing them is $\frac{3}{28}$ .

Q: How do I calculate the probability of pulling out a 3 first?

A: To calculate the probability of pulling out a 3 first, you need to divide the number of 3's by the total number of cards. In this case, there are 3 3's and 8 cards in total, so the probability of pulling out a 3 first is $\frac{3}{8}$ .

Q: How do I calculate the probability of pulling out a 2 second?

A: To calculate the probability of pulling out a 2 second, you need to divide the number of 2's by the total number of cards after pulling out a 3. In this case, there are 2 2's and 7 cards left after pulling out a 3, so the probability of pulling out a 2 second is $\frac{2}{7}$ .

Q: Why do I need to multiply the probabilities of each event together?

A: You need to multiply the probabilities of each event together because the events are dependent on each other. In this case, the probability of pulling out a 2 second depends on the fact that a 3 was pulled out first.

Q: What is the difference between conditional probability and unconditional probability?

A: Conditional probability is the probability of an event occurring given that another event has occurred. Unconditional probability is the probability of an event occurring without any conditions.

Q: Can I use the same formula to calculate the probability of pulling out a 2 first and then a 3?

A: Yes, you can use the same formula to calculate the probability of pulling out a 2 first and then a 3. However, the probability of pulling out a 2 first is $\frac{2}{8}$ , and the probability of pulling out a 3 second is $\frac{3}{7}$ .

Q: How do I calculate the probability of pulling out a specific card from a deck of cards?

A: To calculate the probability of pulling out a specific card from a deck of cards, you need to divide the number of that card by the total number of cards.

Q: Can I use the same formula to calculate the probability of rolling a specific number on a die?

A: Yes, you can use the same formula to calculate the probability of rolling a specific number on a die. However, the probability of rolling a specific number is $\frac{1}{6}$ for a fair six-sided die.

Q: What is the difference between a probability and a chance?

A: A probability is a measure of the likelihood of an event occurring, while a chance is a subjective measure of the likelihood of an event occurring.

Q: Can I use the same formula to calculate the probability of drawing a specific card from a deck of cards?

A: Yes, you can use the same formula to calculate the probability of drawing a specific card from a deck of cards. However, the probability of drawing a specific card is $\frac{1}{52}$ for a standard deck of 52 cards.

Conclusion

In conclusion, this Q&A article provides answers to common questions related to probability and conditional probability. The key to solving these problems is to understand the concept of conditional probability and how it can be used to calculate the probability of a specific sequence of events.