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An urn contains six chips, numbered 1 through 6 . Two are chosen at random and their numbers are added together. What is the probability that the resulting sum is equal to \(5 ?\)

Short Answer

Expert verified
The probability that the sum of the numbers of two randomly chosen chips is 5 is \( \frac{4}{15} \).

Step by step solution

01

Total number of Possible Outcomes

We are selecting two chips out of six. This can be done in \(\binom{6}{2} = 15\) ways. So, the total number of possible outcomes is 15.
02

Favorable Outcomes

The combinations of two chips' numbers that sum to 5 are (1,4), (2,3), (3,2), (4,1). This means there are 4 favorable outcomes.
03

Probability Calculation

The probability of an event is defined as the ratio of the number of favorable outcomes to the total number of outcomes. Thus, the required probability = \( \frac{4}{15} \).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Combinatorics
Combinatorics is a branch of mathematics focused on counting methods, arrangements, and combinations. In this exercise, we use combinatorics to determine the number of ways to select two chips from an urn containing six chips numbered 1 through 6.
Instead of examining every possible pair, combinatorics facilitates finding the total number of possible selections using combinations.
  • Combinations: This refers to selecting items from a group where the order doesn't matter. In our exercise, we're interested in selecting 2 chips from 6, irrelevant to the order of selection.
  • The formula for combinations is represented by \( \binom{n}{k} \), where **n** is the total number of items, and **k** is the number of items to choose. For our exercise, we calculate \( \binom{6}{2} \), representing the ways to choose 2 chips out of 6.
Evaluating \( \binom{6}{2} \) involves calculating \( \frac{6!}{2!(6-2)!} = 15 \). This means there are 15 potential outcomes when picking any 2 of the 6 chips without regard to the order they are selected.
Random Selection
Random selection in probability theory implies that every outcome has an equal chance of occurring. In this exercise, each pair of chips has an equal probability of being selected from the urn, ensuring a fair and unbiased process.
  • Understanding Randomness: Each chip from 1 to 6 holds the same likelihood of being drawn since selection is random. There is no influence or pattern determining which numbers appear in our selection, making it an unbiased process.
  • Simplifying Assumptions: We assume the chips are perfectly mixed, and each draw is independent of previous draws. These assumptions help maintain the integrity of randomness in the process.
This balanced approach allows us to fairly consider all potential pairs and solely focus on the combinations where their sum equals 5, without worrying about any intervention or pattern in selection.
Probability Calculation
Probability is a measure of how likely an event is to happen; it is the ratio of favorable outcomes to the total outcomes. In this exercise, our task is to calculate the probability of the sum of numbers on two chosen chips equaling 5.
  • Enumerating Favorable Outcomes: First, identify which pairs of numbers between 1 and 6 sum up to 5. The pairs are (1,4), (2,3), (3,2), and (4,1), accounting for each possible way to achieve the sum of 5.
  • Calculating Probability: We've established there are 4 favorable outcomes and 15 possible total outcomes from our combination analysis. Therefore, the probability of drawing two chips whose numbers sum to 5 is \( \frac{4}{15} \).
Understanding and calculating such probabilities is an essential skill in probability theory, allowing for the prediction and understanding of random events in a structured manner.

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Most popular questions from this chapter

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