Questions: Counting and Probability
Introduction to permutations and combinations
Suppose we want to choose 2 objects, without replacement, from the 4 objects pencil, eraser, desk, and chair
(a) How many ways can this be done, if the order of the choices is relevant?
(b) How many ways can this be done, if the order of the choices is not relevant?
Transcript text: Counting and Probability
Introduction to permutations and combinations
Suppose we want to choose 2 objects, without replacement, from the 4 objects pencil, eraser, desk, and chair
(a) How many ways can this be done, if the order of the choices is relevant?
(b) How many ways can this be done, if the order of the choices is not relevant?
Solution
Solution Steps
Step 1: Identify the Problem Type
Given the order of selection is relevant, we are dealing with a permutations problem.
Step 2: Apply the Permutations Formula
The formula for permutations is given by \(P(n, k) = \frac{n!}{(n-k)!}\).
Step 3: Substitute the Values \(n = 4\) and \(k = 2\)
Calculation: \(P(4, 2) = \frac{4!}{(4-2)!} = 12\)
Final Answer: The number of ways to choose 2 objects from 4 distinct objects is 12.
Step 1: Identify the Problem Type
Given the order of selection is not relevant, we are dealing with a combinations problem.
Step 2: Apply the Combinations Formula
The formula for combinations is given by \(C(n, k) = \frac{n!}{k!(n-k)!}\).
Step 3: Substitute the Values \(n = 4\) and \(k = 2\)