Home
Class 12
MATHS
Find n and r if ""^nPr=1680,""^nCr=70....

Find n and r if `""^nP_r=1680,""^nC_r=70.`

Promotional Banner

Topper's Solved these Questions

  • MATRICES

    MBD PUBLICATION|Exercise QUESTION BANK|139 Videos

  • PRINCIPLES OF MATHEMATICAL INDUCTION

    MBD PUBLICATION|Exercise QUESTION BANK|16 Videos

Similar Questions

Explore conceptually related problems

Find the value of "^nC_(r-1)//"^nC_r

Find r if: 16P(15,r)= 13P(16,r)

Find r if -501 in[r]_5 .

Find r if P (20,r)=13.P(20,r-1).

Compute P for n=10,r=3

Let A = {1,2,3,4,…., 15,16} and let R be a relation in A given by R={(a,b)}:b=a^(2)} , then find domain and range of relation R.

Let R be a relation in the set of natural numbers N defined by xRy if and only if x+y=18 . Is R an equivalence relation?

Find gof and fog, if f: R rarr R and g: R rarr R are given by f(x) = cos x and g(x) = 3x^(2) , then show that gof ne fog.

Let f : R rarr R be a function given by f(x) = px +q AA x in R . Find constants p and q such that fof = I_(R)

Compute P for n=8,r=4

MBD PUBLICATION-PERMUTATIONS AND COMBINATIONS-QUESTION BANK
  1. Solve ""^nC4=""^nC11,

    Text Solution

    |

  2. Solve ""^(2n)C3:""^nC3=44:5

    Text Solution

    |

  3. Find n and r if ""^nPr=1680,""^nCr=70.

    Text Solution

    |

  4. How many diagonals can an n-gon (a polygon with n sides ) have ?

    Text Solution

    |

  5. If a set A has n elements and another set B has m elements, what is th...

    Text Solution

    |

  6. From five consonants and four vowels, how many words consist of three ...

    Text Solution

    |

  7. In how many ways can a committee of four gentlemen and three ladies b...

    Text Solution

    |

  8. A bag contains 4 black and 5 white balls out of which 6 balls are draw...

    Text Solution

    |

  9. How many triangles can be drawn by joining the vertices of a decagon ?

    Text Solution

    |

  10. How many triangles can be drawn by joining the vertices and the centre...

    Text Solution

    |

  11. Sixty points lie on a plane, out of which no three points are collinea...

    Text Solution

    |

  12. In how many ways can 10 boys and 10 girls sit in a row so that no two ...

    Text Solution

    |

  13. In how many ways can six men and seven girls sit in a row so that the ...

    Text Solution

    |

  14. How many factors does 1155 have that are divisible by 3?

    Text Solution

    |

  15. How many factors does 210 have ?

    Text Solution

    |

  16. If n is a product of k distinct primes what is the total number of fac...

    Text Solution

    |

  17. If m has the prime factor decomposition P1^(r1),P2^(r2)…….Pn^(rn),what...

    Text Solution

    |

  18. If 20! Were multiplied out, how many consecutive zeros would it have o...

    Text Solution

    |

  19. How many factors of 10,000 end with a 5 on the right ?

    Text Solution

    |

  20. A man has 6 friends. In how many ways can he invite two or more to a d...

    Text Solution

    |