Probability of Drawing Two Red Marbles

Oct 13, 2025 by pinkandtrash.com 123 views

Suppose a Jar Contains 7 Red Marbles and 18 Blue Marbles: Finding the Probability of Drawing Two Red Marbles

In this article, we will explore the concept of probability and how to calculate the likelihood of drawing two red marbles from a jar containing 7 red marbles and 18 blue marbles. Probability is a fundamental concept in mathematics that deals with the chance or likelihood of an event occurring. It is a measure of the uncertainty of an event and is often expressed as a number between 0 and 1, where 0 represents an impossible event and 1 represents a certain event.

Let's start by understanding the problem at hand. We have a jar that contains 7 red marbles and 18 blue marbles, making a total of 25 marbles. We are interested in finding the probability of drawing two red marbles from the jar at the same time. This is a classic problem of conditional probability, where the probability of drawing a second red marble depends on the outcome of the first draw.

To calculate the probability of drawing two red marbles, we need to consider the total number of possible outcomes and the number of favorable outcomes. The total number of possible outcomes is the number of ways we can draw 2 marbles from the jar, which is given by the combination formula:

nCk = n! / (k!(n-k)!)

where n is the total number of marbles (25), k is the number of marbles we are drawing (2), and ! denotes the factorial function.

nCk = 25! / (2!(25-2)!) = 25! / (2!23!) = (25 × 24) / (2 × 1) = 300

So, there are 300 possible outcomes when drawing 2 marbles from the jar.

Favorable Outcomes

Now, let's consider the number of favorable outcomes, which is the number of ways we can draw 2 red marbles from the jar. Since there are 7 red marbles, the number of ways we can draw 2 red marbles is given by the combination formula:

nCk = 7! / (2!(7-2)!) = 7! / (2!5!) = (7 × 6) / (2 × 1) = 21

So, there are 21 favorable outcomes when drawing 2 red marbles from the jar.

Probability of Drawing Two Red Marbles

Now that we have the total number of possible outcomes and the number of favorable outcomes, we can calculate the probability of drawing two red marbles. The probability is given by the ratio of the number of favorable outcomes to the total number of possible outcomes:

P(2 red marbles) = Number of favorable outcomes / Total number of possible outcomes = 21 / 300 = 0.07

So, the probability of drawing two red marbles from the jar is 0.07 or 7%.

In this article, we explored the concept of probability and how to calculate the likelihood of drawing two red marbles from a jar containing 7 red marbles and 18 blue marbles. We used the combination formula to calculate the total number of possible outcomes and the number of favorable outcomes, and then calculated the probability of drawing two red marbles. The probability was found to be 0.07 or 7%.

The concept of probability has numerous real-world applications in fields such as finance, insurance, and engineering. For example, in finance, probability is used to calculate the likelihood of a stock price increasing or decreasing, while in insurance, probability is used to calculate the likelihood of a person filing a claim. In engineering, probability is used to calculate the likelihood of a system failing or functioning correctly.

When calculating probability, it's essential to avoid common mistakes such as:

Not considering the total number of possible outcomes
Not considering the number of favorable outcomes
Not using the correct formula for calculating probability
Not rounding the probability to the correct decimal place

When calculating probability, here are some tips and tricks to keep in mind:

Always use the combination formula to calculate the total number of possible outcomes
Always consider the number of favorable outcomes
Always use the correct formula for calculating probability
Always round the probability to the correct decimal place

In conclusion, the concept of probability is a fundamental concept in mathematics that deals with the chance or likelihood of an event occurring. Calculating probability involves considering the total number of possible outcomes and the number of favorable outcomes, and then using the correct formula to calculate the probability. By following the tips and tricks outlined in this article, you can ensure that you are calculating probability correctly and avoiding common mistakes.
Suppose a Jar Contains 7 Red Marbles and 18 Blue Marbles: Finding the Probability of Drawing Two Red Marbles

Q: What is the probability of drawing two red marbles from a jar containing 7 red marbles and 18 blue marbles?

A: The probability of drawing two red marbles from a jar containing 7 red marbles and 18 blue marbles is 0.07 or 7%. This is calculated by dividing the number of favorable outcomes (21) by the total number of possible outcomes (300).

Q: What is the total number of possible outcomes when drawing 2 marbles from a jar containing 25 marbles?

A: The total number of possible outcomes when drawing 2 marbles from a jar containing 25 marbles is 300. This is calculated using the combination formula:

nCk = n! / (k!(n-k)!) = 25! / (2!(25-2)!) = (25 × 24) / (2 × 1) = 300

Q: What is the number of favorable outcomes when drawing 2 red marbles from a jar containing 7 red marbles?

A: The number of favorable outcomes when drawing 2 red marbles from a jar containing 7 red marbles is 21. This is calculated using the combination formula:

nCk = 7! / (2!(7-2)!) = 7! / (2!5!) = (7 × 6) / (2 × 1) = 21

Q: What is the probability of drawing two blue marbles from a jar containing 18 blue marbles and 7 red marbles?

A: The probability of drawing two blue marbles from a jar containing 18 blue marbles and 7 red marbles is 0.93 or 93%. This is calculated by dividing the number of favorable outcomes (171) by the total number of possible outcomes (300).

Q: How do I calculate the probability of drawing two marbles of a specific color from a jar containing multiple colors?

A: To calculate the probability of drawing two marbles of a specific color from a jar containing multiple colors, you need to follow these steps:

Calculate the total number of possible outcomes using the combination formula.
Calculate the number of favorable outcomes by multiplying the number of marbles of the specific color by the number of ways you can draw 2 marbles from the jar.
Divide the number of favorable outcomes by the total number of possible outcomes to get the probability.

Q: What is the difference between probability and odds?

A: Probability and odds are related but distinct concepts. Probability is a measure of the likelihood of an event occurring, expressed as a number between 0 and 1. Odds, on the other hand, are a measure of the ratio of the number of favorable outcomes to the number of unfavorable outcomes.

Q: How do I calculate the probability of drawing two marbles of different colors from a jar containing multiple colors?

A: To calculate the probability of drawing two marbles of different colors from a jar containing multiple colors, you need to follow these steps:

Calculate the total number of possible outcomes using the combination formula.
Calculate the number of favorable outcomes by multiplying the number of marbles of the first color by the number of marbles of the second color and the number of ways you can draw 2 marbles from the jar.
Divide the number of favorable outcomes by the total number of possible outcomes to get the probability.

In this article, we have answered some of the most frequently asked questions about calculating the probability of drawing two marbles from a jar containing multiple colors. We have also provided tips and tricks for calculating probability and avoiding common mistakes. By following the steps outlined in this article, you can ensure that you are calculating probability correctly and making informed decisions.