Textbook Question
Matching Probabilities In Exercises 11-16, match the event with its probability.
a. 0.95
b. 0.005
c. 0.25
d. 0
e. 0.375
f. 0.5
16. You toss a coin four times. What is the probability of tossing tails exactly half of the time?
4. Probability
Counting
1:25 minutesProblem 3.4.15
Textbook Question
In Exercises 15-18, determine whether the situation involves permutations, combinations, or neither. Explain your reasoning.
15. The number of ways 16 floats can line up in a row for a parade
Verified step by step guidance1
Identify the key elements of the problem: The problem involves arranging 16 floats in a specific order for a parade. This indicates that the order of arrangement is important.
Recall the definition of permutations: A permutation is used when the order of arrangement matters. The formula for permutations of n items is n! (n factorial), which represents the product of all positive integers from 1 to n.
Determine whether the problem involves permutations, combinations, or neither: Since the order of the floats in the parade matters, this situation involves permutations.
Write the formula for the number of permutations: The number of ways to arrange 16 floats in a row is given by 16! (16 factorial).
Explain the reasoning: The problem involves arranging all 16 floats in a specific order, and since order matters, it is a permutation problem. The solution is calculated using the factorial of 16.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Permutations
Permutations refer to the arrangement of items in a specific order. When the order of selection matters, such as lining up floats for a parade, we use permutations. The formula for permutations of 'n' items taken 'r' at a time is n! / (n - r)!, where '!' denotes factorial, the product of all positive integers up to 'n'.
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Combinations
Combinations involve selecting items without regard to the order of selection. This concept is used when the arrangement does not matter, such as choosing a committee from a group. The formula for combinations of 'n' items taken 'r' at a time is n! / [r!(n - r)!], highlighting that the order of selection is irrelevant.
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Factorial
Factorial, denoted as 'n!', is a mathematical operation that multiplies a number by all positive integers less than it. It is fundamental in both permutations and combinations, as it helps calculate the total arrangements or selections of items. For example, 5! equals 5 × 4 × 3 × 2 × 1 = 120, which is crucial for determining the number of ways to arrange or select items.
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