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If ^(56)P(r+6):^(54)P(r+3)=30800 :1, fi...

If ` ^(56)P_(r+6):^(54)P_(r+3)=30800 :1,` find `r`.

A

40

B

41

C

42

D

none of these

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The correct Answer is:
B
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OBJECTIVE RD SHARMA ENGLISH-PERMUTATIONS AND COMBINATIONS-Exercise
  1. If (n-1) C6 + (n-1)C7 > nC6 then

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  2. Which of the following is incorrect?

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  3. If ^(56)P(r+6):^(54)P(r+3)=30800 :1, find r.

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  4. The value of sum(r=0)^(m)""^(n+r)C(n) is equal to :

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  5. Every two persons shakes hands with each other in a party and the tot...

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  6. On the occasion if Deepawali festival, each student in a class sends g...

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  7. If ^n+2C8:^(n-2)P4: 57 : 16 , find ndot

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  8. Find the exponent of 3 in 100!

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  9. Ten different letters of an alphabet are given. Words with five letter...

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  10. If 7 points out of 12 are in the same straight line, then the number o...

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  11. about to only mathematics

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  12. No. of diagonals of a polygon are 170. No. of sides in this polygon ar...

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  13. The number of all possible selections of one or more questions from 10...

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  14. The number of ways of painting the faces of a cube with six diffe...

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  15. A box contains 4 white balls, 5 black balls and 2 red balls. The numbe...

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  16. Find the number of different permutations of the letters of the word ...

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  17. A person tries to form as many different parties as he can, out of his...

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  18. Find the number of ways in which 8 different flowered can be strung to...

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  19. The number of words which can be formed out of the letters a, b, c, d,...

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  20. The smallest value of x satisfying the inequality ""^(10)C(x-1)gt2.""^...

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