Probability of person who sit in a circle

In summary, the problem is to find the number of ways a committee of 3 teachers and 4 parents can sit around a round table with 7 seats labeled from A to G. The answer for (i) with no restrictions is 7!=5040. For (ii) with all teachers sitting together, the answer is 1008. To arrive at this answer, first count the number of ways to pick a block of 4 adjacent chairs, then multiply by the number of ways to arrange the 4 teachers and 3 parents in the remaining 3 seats. The correct working for this is 3! x 5! = 720, where the teachers are treated as a single entity and the parents are arranged as
  • #1
desmond iking
284
2

Homework Statement



there are 7 seats around a round table, and is labelled form A to G. Find the number of ways a committee of 3 teachers and 4 parents can sit around the table?

(i ) there is no restriction
my ans is 7!=5040

(ii) all teachers must sit together
the ans is 1008. can someone explain part ii please? my wokring is (6!/(3! x 4!) ) x 4! = 120...

Homework Equations





The Attempt at a Solution

 
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  • #2
desmond iking said:

Homework Statement



there are 7 seats around a round table, and is labelled form A to G. Find the number of ways a committee of 3 teachers and 4 parents can sit around the table?

(i ) there is no restriction
my ans is 7!=5040

(ii) all teachers must sit together
the ans is 1008. can someone explain part ii please? my wokring is (6!/(3! x 4!) ) x 4! = 120...

Homework Equations





The Attempt at a Solution


What's your logic for that working? First count the number of ways to pick a block of 4 adjacent chairs, then multiply by the number of ways you can seat the 4 teachers there and the three parents in the remaining 3 seats.
 
  • #3
sorry my working should be 3! x 5! = 720 which means i arrange the teacher in 3 ! ways first , then i arrange the whole set of teacher into another 5! ways.
 
  • #4
desmond iking said:
sorry my working should be 3! x 5! = 720 which means i arrange the teacher in 3 ! ways first , then i arrange the whole set of teacher into another 5! ways.
Guessing here, but I think what you mean is that having fixed the order of the 3 teachers you treat them as a single entity. So now you have four parents and a block of teachers.
That doesn't quite work. Say you put the teacher block 'at' A. Is that at ABC, or GAB or FGA?
Having got the 3! for the block of teachers, think about how to arrange the parents as a block, then how to match the two blocks to the 7 chairs.
 

FAQ: Probability of person who sit in a circle

What is the probability of a person sitting in a certain position in a circle?

The probability of a person sitting in a specific position in a circle depends on the total number of people in the circle and the number of positions available. For example, if there are 10 people in the circle and 10 positions available, the probability of a person sitting in a specific position is 1/10 or 10%.

How does the number of people in a circle affect the probability of a person sitting in a certain position?

The number of people in a circle directly affects the probability of a person sitting in a certain position. As the number of people increases, the total number of positions available decreases, therefore decreasing the probability of a person sitting in a specific position.

Does the shape of the circle affect the probability of a person sitting in a certain position?

Yes, the shape of the circle can affect the probability of a person sitting in a certain position. For example, if the circle is a regular polygon with an even number of sides, the probability of a person sitting in the center position is higher compared to a circle with an odd number of sides.

How does the position of the first person chosen affect the probability of the other people sitting in a circle?

The position of the first person chosen does not affect the probability of the other people sitting in a circle. The probability remains the same regardless of the initial position chosen.

Can the probability of a person sitting in a circle be calculated mathematically?

Yes, the probability of a person sitting in a circle can be calculated using the formula P = 1/n, where P is the probability and n is the total number of positions available in the circle. However, this formula assumes that all positions are equally likely to be chosen.

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