Chapter 20: Problem 28
In how many ways can a committee consisting of 3 men and 4 women be formed from a group of 6 men and 7 women? (1) \({ }^{6} \mathrm{C}_{-}^{7} \mathrm{C}\) (2) \({ }^{6} \mathrm{C}^{7} \mathrm{C}\) (3) \({ }^{6} \mathrm{C}_{[}^{7} \mathrm{C}\) (4) ' \(\mathrm{C}^{6} \mathrm{C}\)
Short Answer
Expert verified
Answer: A committee consisting of 3 men and 4 women can be formed in 700 different ways.
Step by step solution
01
Combination Formula
To solve this problem we need to use the combination formula, which is
\(\,_{n}C_{r}=\frac{n!}{r!(n-r)!}\)
where \(_{n}C_{r}\) is the number of combinations of n elements taken r at a time, n is the total number of elements, r is the number of elements to choose, and ! denotes the factorial function.
02
Selecting 3 Men from 6 Men
Apply the combination formula to select 3 men from 6 men:
\(\,_{6}C_{3}=\frac{6!}{3!(6-3)!}\)
03
Calculating the Number of Ways to Select 3 Men
Calculate the result:
\(\,_{6}C_{3}=\frac{6!}{3!3!}=\frac{6\times5\times4}{3\times2\times1} = 20\)
So, there are 20 ways to select 3 men from 6 men.
04
Selecting 4 Women from 7 Women
Apply the combination formula to select 4 women from 7 women:
\(\,_{7}C_{4}=\frac{7!}{4!(7-4)!}\)
05
Calculating the Number of Ways to Select 4 Women
Calculate the result:
\(\,_{7}C_{4}=\frac{7!}{4!3!}=\frac{7\times6\times5}{3\times2\times1} = 35\)
So, there are 35 ways to select 4 women from 7 women.
06
Total Ways to Form the Committee
To find the total number of possible ways to form a committee consisting of 3 men and 4 women, multiply the number of ways of selecting men and women:
Total ways = (Ways to select 3 men) × (Ways to select 4 women)
Total ways = 20 × 35 = 700
Therefore, a committee consisting of 3 men and 4 women can be formed in 700 ways.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Combination Formula
The combination formula is a powerful tool in combinatorics. It helps determine the number of ways to select a group from a larger set, without caring about the order of selection. This is particularly useful when dealing with problems that involve group formation. The formula is given by: \[_{n}C_{r} = \frac{n!}{r!(n-r)!}\]In this formula,
- \(n\) represents the total number of items
- \(r\) is the number of items we want to choose
- \(!\) is the factorial symbol, which multiplies a series of descending natural numbers
Factorial Concept
Factorials are a fundamental concept in mathematics, often used within the combination formula. The notation \( n! \) denotes a factorial, which is the product of all positive integers up to \(n\). For example,
- \(5! = 5 \times 4 \times 3 \times 2 \times 1 = 120\)
- \(3! = 3 \times 2 \times 1 = 6\)
- \(1! = 1\)
- By definition, \(0! = 1\)
Committee Selection
Committee selection problems are a common application of combinatorics. They involve selecting a subgroup from a larger set, just like forming a committee from a group of people. This specific problem illustrates how to select members based on specific requirements, such as choosing 3 men from 6 and 4 women from 7.To solve such problems, follow these steps:
- Use the combination formula to calculate the number of ways to choose the required number of members from each subset.
- For example, choose 3 men from 6, which is calculated as \(\,_{6}C_{3}\), and 4 women from 7, which is \(\,_{7}C_{4}\).
- Multiply the number of ways to get the total number of ways to form the committee.
Mathematical Problem Solving
Mathematical problem solving with combinatorics often involves a step-by-step approach to break down complex problems into more manageable parts. Here's a simple guide to tackling such problems:
- Clearly understand what is being asked. Identify the elements and the selections needed.
- Recognize whether the problem involves combination (order doesn't matter) or permutation (order matters).
- Write down the appropriate formula, like the combination formula in this case.
- Substitute the given numbers into the formula to calculate.
- For multiple requirements in a problem, calculate each separately and ensure to combine them correctly, often by multiplication.