English

If Nc12 = Nc8 , Then N = (A) 20 (B) 12 (C) 6 (D) 30 - Mathematics

Advertisements
Advertisements

Question

If nC12 = nC8 , then n =

Options

  • 20

  • 12

  • 6

  • 30

MCQ
Advertisements

Solution

20

\[n = 12 + 8 = 20\]  [∵ \[{}^n C_x =^n C_y \Rightarrow n = x + y or x = y\]]
shaalaa.com
  Is there an error in this question or solution?
Chapter 17: Combinations - Exercise 17.5 [Page 25]

APPEARS IN

RD Sharma Mathematics [English] Class 11
Chapter 17 Combinations
Exercise 17.5 | Q 7 | Page 25

Video TutorialsVIEW ALL [1]

RELATED QUESTIONS

In how many ways can one select a cricket team of eleven from 17 players in which only 5 players can bowl if each cricket team of 11 must include exactly 4 bowlers?


A bag contains 5 black and 6 red balls. Determine the number of ways in which 2 black and 3 red balls can be selected.


A committee of 7 has to be formed from 9 boys and 4 girls. In how many ways can this be done when the committee consists of:

(i) exactly 3 girls?

(ii) atleast 3 girls?

(iii) atmost 3 girls?


Compute:

 L.C.M. (6!, 7!, 8!)


There are four parcels and five post-offices. In how many different ways can the parcels be sent by registered post?


A letter lock consists of three rings each marked with 10 different letters. In how many ways it is possible to make an unsuccessful attempt to open the lock?


How many A.P.'s with 10 terms are there whose first term is in the set {1, 2, 3} and whose common difference is in the set {1, 2, 3, 4, 5}?


How many odd numbers less than 1000 can be formed by using the digits 0, 3, 5, 7 when repetition of digits is not allowed?


If nC4 = nC6, find 12Cn.


If 15Cr : 15Cr − 1 = 11 : 5, find r.


From a group of 15 cricket players, a team of 11 players is to be chosen. In how many ways can this be done?


In how many ways can a football team of 11 players be selected from 16 players? How many of these will

include 2 particular players?


How many different selections of 4 books can be made from 10 different books, if
two particular books are always selected;


How many different selections of 4 books can be made from 10 different books, if two particular books are never selected?


From 4 officers and 8 jawans in how many ways can 6 be chosen. to include at least one officer?


How many triangles can be obtained by joining 12 points, five of which are collinear?


A group consists of 4 girls and 7 boys. In how many ways can a team of 5 members be selected if the team has (i) no girl?


In how many ways can a team of 3 boys and 3 girls be selected from 5 boys and 4 girls?


Find the number of ways of selecting 9 balls from 6 red balls, 5 white balls and 5 blue balls if each selection consists of 3 balls of each colour.


A committee of 7 has to be formed from 9 boys and 4 girls. In how many ways can this be done when the committee consists of: atmost 3 girls?


5C1 + 5C2 5C3 + 5C4 +5C5 is equal to


The number of diagonals that can be drawn by joining the vertices of an octagon is


There are 3 wicketkeepers and 5 bowlers among 22 cricket players. A team of 11 players is to be selected so that there is exactly one wicketkeeper and at least 4 bowlers in the team. How many different teams can be formed?


If α = mC2, then αCis equal to.


The value of `(""^9"C"_0 + ""^9"C"_1) + (""^9"C"_1 + ""^9"C"_2) + ... + (""^9"C"_8 + ""^9"C"_9)` is ______ 


In a small village, there are 87 families, of which 52 families have atmost 2 children. In a rural development programme 20 families are to be chosen for assistance, of which atleast 18 families must have at most 2 children. In how many ways can the choice be made?


In how many ways a committee consisting of 3 men and 2 women, can be chosen from 7 men and 5 women?


All the letters of the word ‘EAMCOT’ are arranged in different possible ways. The number of such arrangements in which no two vowels are adjacent to each other is ______.


A box contains two white, three black and four red balls. In how many ways can three balls be drawn from the box, if atleast one black ball is to be included in the draw


In how many ways can a football team of 11 players be selected from 16 players? How many of them will include 2 particular players?


Total number of words formed by 2 vowels and 3 consonants taken from 4 vowels and 5 consonants is equal to ______.


Three balls are drawn from a bag containing 5 red, 4 white and 3 black balls. The number of ways in which this can be done if at least 2 are red is ______.


Eighteen guests are to be seated, half on each side of a long table. Four particular guests desire to sit on one particular side and three others on other side of the table. The number of ways in which the seating arrangements can be made is `(11!)/(5!6!) (9!)(9!)`.


The value of `""^50"C"_4 + sum_("r" = 1)^6 ""^(56 - "r")"C"_3` is ______.


If number of arrangements of letters of the word "DHARAMSHALA" taken all at a time so that no two alike letters appear together is (4a.5b.6c.7d), (where a, b, c, d ∈ N), then a + b + c + d is equal to ______.


A badminton club has 10 couples as members. They meet to organise a mixed double match. If each wife refers to p artner as well as oppose her husband in the match, then the number of different ways can the match off will be ______.


The number of numbers between 2,000 and 5,000 that can be formed with the digits 0, 1, 2, 3, 4, (repetition of digits is not allowed) and are multiple of 3 is?


A regular polygon has 20 sides. The number of triangles that can be drawn by using the vertices but not using the sides is


Share
Notifications

Englishहिंदीमराठी


      Forgot password?
Use app×