An event is attended by 8 guests – 5 men and 3 women. 8 chairs a...
Since order matters in this question (Seats A, B and C occupied with John, Graham and Paul is a different seating arrangement from Seats A, B and C occupied with Graham, Paul and John), we can solve it using either the Filling Spaces method or the Permutation formula.
Step 1: Understand the objective
The objective of the question here is to find the number of ways in which the 8 guests can be seated on 8 seats. Since the seats for men and women are fixed (Seats A-E are the 5 seats reserved for men and Seats F-H are the three seats reserved for women), the objective actually becomes: to find the number of ways in which 5 men can be arranged on 5 seats and 3 women can be arranged on 3 seats.
Step 2: Write the objective equation enlisting all tasks
The objective here consists of two tasks:
- Task 1-Arrange 5 men on 5 seats (Seats marked A-E)
- Task 2 – Arrange 3 women on 3 seats (Seats marked F-H)
Now that we have enlisted the tasks, we need to determine whether the number of ways of doing these two tasks should be added or multiplied.
Let’s look at the objective statement:
“To find the number of ways in which 5 men can be arranged on 5 seats and 3 women can be arranged on 3 seats.”
The objective statement contains the word AND between the two tasks. This means that we put a multiplication sign in the objective equation.
Thus, the objective equation will be:
Now, we know that
The number of ways in which 5 men can be arranged in 5 seats = 5P5
And
The number of ways in which 3 women can be arranged in 3 seats = 3P3
So, the objective equation becomes:
(Number of ways of arranging the 8 people on the 8 seats) = 5P5 x 3P3
Step 3: Determine the number of ways of doing each task
In Step 3, using the Permutation Formula (nPn = n!), we get that
5P5 = 5! = 5*4*3*2*1 = 120
And,
3P3 = 3! = 3*2*1 = 6
Step 4: Calculate the final answer
By putting these valuesin the objective equation, we get:
(Number of ways of arranging the 8 people on the 8 seats) = 120 x 6 = 720
Looking at the answer choices, we see that Option D is correct.