## yrelhan4 2 years ago If 7 smallest squares are chosen at random from a chessboard then the probability that they lie on diagonal, is ?

1. yrelhan4

@shubhamsrg

2. yrelhan4

@DLS

3. DLS

smallest square?

4. DLS

nahi,nahi ho sakta :O galat question hai :|

5. yrelhan4

nvm. i think... i got it. http://www.allinterview.com/showanswers/8354.html

6. yrelhan4

But a better explanation would be even better..

7. DLS

There are total of 64 blocks on a chessboard. So 3 blocks can be chosen out of 64 in 64C3 ways. So the sample space is = 41664 There are 2 diagonal on chessboard each one having 8 blocks. Consider one of them. 3 blocks out of 8 blocks in diagonal can be chosen in 8C3 ways. But there are 2 such diagonals, hence favourables = 2 * 8C3 = 2 * 56 = 112 The require probability is = 112 / 41664 = 1 / 372 = 0.002688

8. DLS

hope u got it :)

9. yrelhan4

:/

10. shubhamsrg

7 chosen ki 3 chosen ?

11. yrelhan4

7 choslo..

12. DLS

13. shubhamsrg

oh, 7 choslo hai..hmm mera to 18/C(64,7) aa raha hai :3

14. yrelhan4

umm. upar 20 hai.. 20/64C7..

15. shubhamsrg

ohh :O hmm

16. DLS

merko samaj agaya 20 kyun hai :")

17. DLS

!!!!!!

18. yrelhan4

kyun??

19. DLS

20. shubhamsrg

aa gaya 20 yo maine 1 diagnol miss kar diya tha

21. yrelhan4

abbe koi mereko btayega? :/

22. shubhamsrg

dekho 8 sq. wale 2 diagnols hote hain 7 sq wale 4 diagnols hote hain hai na?

23. DLS

24. DLS

3 tarah se le sakte hai 8c7 lelia aur 7c7 aur 7c7 se bhi

25. DLS

baaki green waaale nahi le sakte 7 nahi hai condition satisfy nahi karte

26. DLS

red waala aur 2 green waale hain acceptable case

27. DLS

so 8c7+7c7+7c7

28. yrelhan4

hmm.. 2(8c7+7c7+7c7) nhi krna chahiye? us figure me / vale diagonals hain.. \ vale diagonals?

29. DLS

wahi to kiya :O

30. DLS

mai sirf bracket ke andar ka part bata raha tha

31. shubhamsrg

kaise kar lete ho @DLS how? :O

32. DLS

mai sirf ek side ka bata raha hoon

33. yrelhan4

ohho.. ok samajh gya. thank you.

34. DLS

induction :")))

35. DLS

sab clear hojaega isse :|