Chapter 9: Problem 7
Find the number. $$P(6,1)$$
Short Answer
Expert verified
There are 6 permutations of 6 items taken 1 at a time.
Step by step solution
01
Understand the notation
The notation \( P(n, r) \) refers to the number of permutations of \( n \) items taken \( r \) at a time. This means we are looking for arrangements of \( r \) items from a set of \( n \) items.
02
Apply the permutation formula
The formula for permutations is given by \( P(n, r) = \frac{n!}{(n-r)!} \). We need to plug in the values \( n = 6 \) and \( r = 1 \) into the formula.
03
Calculate the factorials
Calculate 6! and (6-1)!: \( 6! = 6 \times 5 \times 4 \times 3 \times 2 \times 1 = 720 \) and \( 5! = 5 \times 4 \times 3 \times 2 \times 1 = 120 \).
04
Substitute into the formula
Substitute the calculated factorial values into the formula: \( P(6,1) = \frac{6!}{5!} = \frac{720}{120} \).
05
Simplify the expression
Simplify \( \frac{720}{120} \) to find the result of the permutation. Calculating this gives 6.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Factorial
The factorial of a number is a key component of understanding permutations. The concept "factorial" refers to the product of all positive integers up to that number.
- It is denoted using an exclamation mark: so, \( n! \) means "n factorial".
- For example, \( 5! \) would be calculated as \( 5 \times 4 \times 3 \times 2 \times 1 = 120 \).
- The factorial of 0 is defined to be 1, which can sometimes be surprising!
Permutation Formula
The permutation formula allows us to determine the number of different ways we can arrange or order a set of items. To express it, we use \( P(n, r) \), where \( n \) is the total number of items and \( r \) is the number of items we want to arrange. The formula itself is:\[ P(n, r) = \frac{n!}{(n-r)!} \]
- It essentially considers the total possible arrangements of \( n \) items and then removes the arrangements of \( n-r \) items—those extra positions we do not need.
- If \( r = n \), the formula simplifies to just \( n! \).
- For smaller \( r \) values, like the exercise \( P(6, 1) \), it becomes very simple: it's just \( n \).
Mathematical Notation
Mathematical notation provides a shorthand way to describe mathematical concepts and operations. In the context of permutations, the notation \( P(n, r) \) is particularly important. Here’s a bit more on mathematical notations:
- "\( P \)" stands for "permutation" in this specific notation, indicating that we are calculating permutations.
- The "\( n \)" and "\( r \)" parameters inside the parentheses tell us the total number of items to consider and how many we want to arrange.
- Such notations help mathematicians and learners quickly communicate complex mathematical ideas without lengthy descriptions.