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

Find 'r' when :
(i) `""^(10)P_(r )=2 ""^(9)P_(r )`
(ii) `""^(11)P_(r )= ""^(12)P_(r-1)`.

Text Solution

Verified by Experts

The correct Answer is:
(i) r = 5 (ii) r = 9
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MODERN PUBLICATION-PERMUTATIONS AND COMBINATIONS -OBJECTIVE TYPE QUESTIONS (D) VERY SHORT ANSWER TYPE QUESTIONS
  1. Find the value of 'r' if ""^(5)P(r )=""^(6)P(r-1).

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  2. Evaluate the following : (i) ""^(8)P(5) (ii) ""^(10)P(3) ...

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

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

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

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

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

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

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

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

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

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

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

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

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