Math Problem Statement

Professor Tannen and 9 TAs are preparing for an important conference. They are arranging themselves around a circular table. Two seatings are considered the same if every person has the same left and right neighbors. However, there is a certain constraint to this arrangement: three TAs, Gamma, Delta, and Epsilon, insist on sitting together in a consecutive block (but the order within this block does not matter). How many different seating arrangements satisfy these conditions?

Solution

To solve this problem, we need to determine the number of ways to arrange Professor Tannen and 9 TAs around a circular table, with the constraint that three specific TAs (Gamma, Delta, and Epsilon) must sit together in a consecutive block.

Step 1: Group Gamma, Delta, and Epsilon

Since Gamma, Delta, and Epsilon must sit together, we can treat them as a single "block." This reduces the problem to arranging 7 individual people (Professor Tannen and the remaining 6 TAs) and 1 block around the table.

Step 2: Arranging around a Circular Table

In a circular arrangement, the number of ways to arrange nn distinct objects is (n1)!(n - 1)!. In this case, we have 7 individuals plus 1 block, giving us 8 objects to arrange. The number of ways to arrange these 8 objects around a circular table is:

(81)!=7!(8 - 1)! = 7!

Step 3: Arranging Within the Block

The three TAs (Gamma, Delta, and Epsilon) within the block can be arranged among themselves in any order. Since the order of Gamma, Delta, and Epsilon within the block matters, the number of ways to arrange them is:

3!=63! = 6

Step 4: Combine Arrangements

To find the total number of seating arrangements that satisfy the conditions, we multiply the number of ways to arrange the 8 objects around the table by the number of ways to arrange Gamma, Delta, and Epsilon within their block:

7!×3!=5040×6=302407! \times 3! = 5040 \times 6 = 30240

Therefore, the total number of different seating arrangements that satisfy the conditions is:

30240\boxed{30240}

Would you like further details or have any questions about this problem?

Here are 5 related questions to explore further:

  1. What if the three TAs (Gamma, Delta, and Epsilon) must sit together in a specific order?
  2. How would the solution change if there were more or fewer TAs with similar constraints?
  3. How many arrangements are there if all 10 individuals (including the professor) must sit with a specific neighbor?
  4. What if instead of sitting together, the three TAs want to sit exactly one person apart?
  5. How would the arrangements change if the table were rectangular instead of circular?

Tip: In problems involving circular arrangements, fixing one person's position often simplifies the counting by reducing rotational symmetries!

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Combinatorics
Circular Permutations

Formulas

Number of arrangements for n distinct objects in a circle: (n-1)!
Permutations of a block of k objects: k!

Theorems

Circular Permutation Theorem

Suitable Grade Level

Grades 11-12