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Find the number of permutations of n dis...

Find the number of permutations of n distinct things taken r together, in which 3 parritcular things must occur together.

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The correct Answer is:
`= ((n-3),(r-3))xx (r-2)!xx3!`
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KUMAR PRAKASHAN-PERMUTATIONS AND COMBINATIONS-NCERT EXEMPLAR PROBLEMS (SHORT ANSWER TYPE QUESTIONS)
  1. Eight chairs are numbered 1 to 8. Two women and 3 man wish to occupy o...

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  2. If the letters of the word 'RACHIT' are arranged in all possible ways ...

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  3. A candidate is required to answer 7 questions out of 12 questions, whi...

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  4. Out of 18 points in a plane, no three are in the same line except five...

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  5. We wish tto select 6 person from 8 but, if the person A is chosen, the...

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  6. How many committee of five person with a chairperson can be selected ...

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  7. How many automobile licencse plates can be made, if each plate contain...

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  8. A bag contains 5 black and 6 red balls. Determine the number of ways i...

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  9. Find the number of permutations of n distinct things taken r together,...

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  10. Find the number of different words that can be formed from the letters...

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  11. Find the number of popstive integers greater than 6000 and less than 7...

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  12. There are 10 persons named ""P1,P2,P3,....,P10' Out of 10 persons, 5 p...

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  13. There are 10 lamps in a hall, Each one of them can be switched on inde...

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  14. A box contains two white, there black and four red balls. In how many ...

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  15. if ""^nc(r-1)=36, ""^ncr=84 and ""^nc(r+1)=126,than find the value of ...

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  16. Find the number of integers greater than 7000 that can be formed with ...

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  17. If 20 lines are drawn in a plane such that no two of them are paralled...

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  18. In a certain city, all telephone numbers have six digits , the first t...

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  19. In an examination, a student has to answer 4 questions out of 5 questi...

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  20. If a convex polygon has 44 diagonals, than find the number of its side...

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