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These problems involve distinguishable permutations. Work Assignments Eight workers are cleaning a large house. Five are needed to clean windows, two to clean the carpets, and one to clean the rest of the house. In how many different ways can these tasks be assigned to the eight workers?

Short Answer

Expert verified
There are 168 different ways to assign tasks to the workers.

Step by step solution

01

Understand The Problem

We need to assign 8 workers to 3 different tasks: 5 workers to clean windows, 2 to clean carpets, and 1 to clean the rest of the house. The order in which the workers are assigned to tasks matters, making this a problem of distinguishable permutations.
02

Determine The Total Permutations

First, we calculate the total number of permutations of the 8 workers as if there were no specific tasks. This can be done using the formula for permutations: \[ 8! = 8 \times 7 \times 6 \times 5 \times 4 \times 3 \times 2 \times 1 = 40320 \]
03

Account For Indistinguishable Groups

Since the tasks require specific numbers of workers (5 for windows, 2 for carpets, 1 for the rest of the house), some of these permutations are indistinguishable from one another. We need to divide the total permutations by the permutations of the workers within each group. The formula becomes: \[ \frac{8!}{5! \times 2! \times 1!} \]
04

Calculate The Group Permutations

Calculate the factorial for each group: - For 5 workers cleaning windows: \(5! = 120\)- For 2 workers cleaning carpets: \(2! = 2\)- For 1 worker cleaning the rest: \(1! = 1\). Now substitute these values into the formula: \[ \frac{40320}{120 \times 2 \times 1} \]
05

Simplify The Expression

Simplify the expression by calculating the denominator: \[ 120 \times 2 = 240 \]. Then, divide the total number of permutations by this product: \[ \frac{40320}{240} = 168 \].
06

Conclusion

There are 168 different ways to assign these tasks to the eight workers, taking into account the task requirements for each group.

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Key Concepts

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

Permutations Formula
When exploring how to assign tasks to workers, you'll often find yourself using what's known as the permutations formula. This formula helps us find the number of ways to arrange a set of objects and is crucial in solving problems about tasks and assignment. For organizing a set of objects (in this case, workers), the permutations formula is given by \( n! \), where \( n \) represents the total items to arrange.
This formula is highly applicable when every arrangement of items or people is distinct and needs to be counted separately. For example, if you have 8 workers to assign to different tasks, the number of ways to arrange these workers would be \( 8! \). This results in a large number—40,320—and demonstrates how quickly permutation counts can grow with more items.
Factorial
The word 'factorial' probably sounds complex, but it's simpler than you think! In mathematics, the factorial of a positive integer \( n \), denoted as \( n! \), is the product of all positive integers less than or equal to \( n \).
For example, \( 5! \) ("five factorial") is calculated as \( 5 \times 4 \times 3 \times 2 \times 1 = 120 \). Factorials are useful when you're trying to calculate permutations and combinations. For the eight workers in our problem, \( 8! \) means multiplying all the numbers from 8 down to 1, creating a foundation for determining how many ways we can assign them to tasks.
Task Assignment
Task assignment problems leverage permutation concepts by understanding that not every arrangement is unique due to repeated roles or tasks. You might need to assign workers to roles where certain numbers of workers perform the same task.
In task assignment, you first calculate the total permutations of the workers without splitting them into tasks. Then, by recognizing that groups of workers might be performing indistinguishably equivalent tasks, you divide the total permutations by the factorials of the group sizes. This approach reduces the number of valid task configurations, accounting only for distinguishable ways to assign workers to tasks.
Combinatorics
Combinatorics is the branch of mathematics focused on counting, combination, and arrangement of sets. It's crucial for determining how many ways tasks can be distributed among workers. In our example, it tells us how we can assign these roles without manually listing each possibility.
Why does it matter? Because combinatorics provides methods and formulas that streamline complex counting tasks into manageable problems. With it, you can find solutions to many scenarios where arrangements or distributions are concerned. This includes planning in project management, resource allocation, and organizing schedules efficiently.

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