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n and r integers such that 1lerlen, then...

n and r integers such that `1lerlen`, then n. `""^(n-1)C_(r-1)` is

A

`""^(n)C_(r)`

B

`n.""^(n)C_(r)`

C

`r.""^(n)C_(r)`

D

`(n-1)""^(n)C_(r)`

Text Solution

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The correct Answer is:
C
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AAKASH SERIES-PERMUTATIONS & COMBINATIONS-EXERCISE-I
  1. The number of ways in which four letters can be put in four addressed ...

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  2. The positive integer r, such that ""^(15)C(3r)=""^(15)C(r+3) is equal ...

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  3. n and r integers such that 1lerlen, then n. ""^(n-1)C(r-1) is

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  4. If ""^(n)C(3)=10, then n is

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  5. If ""^(n)C(r) denotes the number of combinations of n things taken r t...

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  6. If ""^(8)C(3)+""^((n+2))C(4)=""^(9)C(4), then n is

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  7. IF C (2n, 3) : C (n,2) = 12 : 1, then n=

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  8. The number of ways in which a team of 6 players can be chosen from 11 ...

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  9. The number of diagonals in a polygon of 10 sides is

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  10. If these are 8 points on a circle, then number of different line seg...

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  11. If these are 8 points on a circle, Number of triangles formed by joi...

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  12. There are 10 parallel lines intersected by a family of 5 parallel line...

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  13. The number of rectangles formed in a chess board is

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  14. Assuming the balls to be identical except for difference in colours, t...

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  15. Numbar of different sums that can be formed with half rupee coin, a tw...

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  16. a man has 4 friends , in how many ways can he inivite one or ...

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  17. The number of divisors of 7! is

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  18. The sum of divisors of 2 ^5 3^4 5^3 is

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  19. The number of ways can 9 things be divided equally among 3 persons is

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  20. The number of ways in which 9 things can be divided into 3 equal group...

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