Permutation and Combination // May 2026

Solving Permutation Problems
Alternating Seating Arrangements

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Understanding the Problem

In this problem, we are tasked with arranging 4 men and 3 women in a row of 7 seats such that men and women alternate. This is a classic combinatorics problem that tests your understanding of arrangement patterns and the Fundamental Counting Principle.

The Logic of Alternating Arrangements

To ensure that men and women alternate in a row of 7 seats, we must look at the available positions.

Since there are more men (4) than women (3), the only possible pattern that allows them to alternate is: M - W - M - W - M - W - M

If we tried to start with a woman, we would run out of women before filling all the 'M' slots. Thus, the men must occupy positions 1, 3, 5, and 7, while the women must occupy positions 2, 4, and 6.

Step-by-Step Solution

Step 1: Arrange the Men

The 4 men can be arranged in the 4 designated positions (1, 3, 5, 7) in $4!$ ways. $4! = 4 \times 3 \times 2 \times 1 = 24$ ways.

Step 2: Arrange the Women

The 3 women can be arranged in the 3 designated positions (2, 4, 6) in $3!$ ways. $3! = 3 \times 2 \times 1 = 6$ ways.

Step 3: Apply the Fundamental Counting Principle

Since these events are independent, we multiply the number of ways to arrange the men by the number of ways to arrange the women: Total ways = $(4!) \times (3!) = 24 \times 6 = 144$.

Conclusion

There are 144 unique ways to seat the 4 men and 3 women such that they alternate positions.

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