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Four persons A, B, C and D are to the se...

Four persons A, B, C and D are to the seated at a circular table. In how many ways can they be seated ?

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To find the number of ways to seat four persons A, B, C, and D at a circular table, we can follow these steps: ### Step 1: Understand Circular Permutations In circular permutations, one position is fixed to avoid counting rotations of the same arrangement multiple times. This is because in a circle, rotating the arrangement does not create a new unique arrangement. ### Step 2: Fix One Person We can fix one person in one position. Let's fix person A at one seat. This means we only need to arrange the remaining three persons (B, C, and D). ### Step 3: Arrange the Remaining Persons Now, we need to arrange the remaining three persons (B, C, and D) around the table. The number of ways to arrange n distinct objects in a line is given by n!. However, since we have fixed one person, we will arrange the remaining (n-1) persons. ### Step 4: Calculate the Factorial For our case, we have: - Total persons = 4 (A, B, C, D) - Fixed person = 1 (A) - Remaining persons = 4 - 1 = 3 (B, C, D) The number of arrangements of the remaining 3 persons is given by: \[ (n-1)! = 3! \] Calculating 3!: \[ 3! = 3 \times 2 \times 1 = 6 \] ### Final Answer Thus, the total number of ways to seat the four persons A, B, C, and D at a circular table is **6**. ---
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MODERN PUBLICATION-PERMUTATIONS AND COMBINATIONS -OBJECTIVE TYPE QUESTIONS (D) VERY SHORT ANSWER TYPE QUESTIONS
  1. Evaluate the following : (i) ""^(8)P(5) (ii) ""^(10)P(3) ...

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  2. Find 'r' when : (i) ""^(10)P(r )=2 ""^(9)P(r ) (ii) ""^(11)P(...

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  3. Find 'n' if 2 ""^(5)P(3)= ""^(n)P(4)

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  4. How many 3-digit even numbers can be formed from the digit 1,2,3,4,5,6...

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  5. How many 3 digit numbers are there, with distinct digits, with each ...

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  6. Find n if .^(n-)P(3): .^(n)P(4) = 1:9.

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  7. Four persons A, B, C and D are to the seated at a circular table. In h...

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  8. In how many ways can 6 beads of same colour form a neclace ?

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  9. If .^(2n)C(3):.^(n)C(3)=12:1, find n.

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  10. If ""^(n)C(8)= ""^(n)C(9), find the value of n.

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  11. If ""^(2n)C(1), ""^(2n)C(2) and ""^(2n)C(3) are in A.P., find n.

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  12. From a class of 32 students, 4 are to be chosen for a competition. In ...

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  13. The no. of ways can 5 sportsmen be selected from a group of 10 sportsm...

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  14. How many selection of 4 books can be made from 8 different books?

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  15. A committee of 2 boys is to be selected from 4 boys. In how many ways ...

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  16. Sudha wants to choose any 9 stamps from a set of 11 different stamps. ...

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  17. How many lines can be drawn through 6 points on a circle ?

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  18. How many triangles can be drawn through n points on a circle ?

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  19. A polygon has 44 diagonals , then the number of its sides is

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  20. In how many ways can 12 things be equally divided among 4 persons ?

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