## virtus 3 years ago find the no. of ways in which 8 people can be seated at 2 round tables with 4 people sitting at each table?

1. Hashir

got it???

2. Hashir

acually its like ... choose four people ...then arrange them .... permutaion means choosing and aranging

3. hba

36

4. Hashir

that dot means multiplty

5. virtus

why does the answer in my solution book say this : 7x6x5x3x2x1x2

6. Hashir

wait a sec .... let me take a look at question again

7. hba

WAIT I HAVE A WAY

8. virtus

@hba having epiphanies are we?

9. hba

IF UR ASKED OF A ROW THEN n! IF UR ASKED ABOUT A CIRCLE OR ROUND ITS (n-1)! AND IF ITS A NECKLACE OR GARLAND ITS 1/2(n-1)!

10. hba

IN UR CASE IT WOULD BE (8-1)! =7!

11. hba

AND 2 TABLES SO U MULTIPLY IT BY 2 THEN

12. Hashir

naaaa

13. hba

Remember that a circular permutation is (n – 1)! Break the seating process into "activities" like this: 1) Choose the people who are seated at each table. C(8,4 = 8•7•6•5/4•3•2•1 = 70). When you choose for 1 table the other four automatically go to the other table. 2) Arrange the 4 people at table A: (4 – 1)! = 3! = 6 3) Arrange the 4 people at table B. Also 3! =6 So answer is C(8,4)•3!•3! = 70•6•6 = 2520

14. Hashir

he copied it from somewhere :D

15. Hashir

anyway ... nice work @hba :D

16. hba

You are free: to Share — to copy, distribute and transmit the work to Remix — to adapt the work

17. Hashir

^^ LOL

18. virtus

hey @hba so you used combinations and not only permutations for this questions?

19. hba

yeah