Sign in
12thPass logo
New chatPYQ LibraryDoubtsRank report
Sign in to see Recents

Your guest activity stays on this device

Sign in to save progress →
Sign in

Permutations and Combinations question

2019 · 12 Jan · Shift 2 · Q27
Guest · filters and generic practice availableBrowsing as a guest · PYQ filters and generic practice are available. Sign in only for personalised features and saved progress.
  1. PYQ Library
  2. /JEE Main
  3. /Mathematics
  4. /Permutations and Combinations
  5. /2019 · 12 Jan · Shift 2 · Q27

Permutations and Combinations question

2019 · 12 Jan · Shift 2 · Q27

JEE MainMathematicsPermutations and CombinationsMCQ+4 / −1
There are m men and two women participating in a chess tournament. Each participant plays two games with every other participant. If the number of games played by the men between themselves exceeds the number of games played between the men and the women by 84, then the value of m is :
  1. A
    12
  2. B
    9
  3. C
    7
  4. D
    11
View written solutionFree

Correct answer: A

  1. Interpret the situation

There are mmm men and 222 women, so total participants are m+2m+2m+2.

Each pair of participants plays 2 games with each other.

We must compare:

  • games played by the men among themselves
  • games played between men and women

It is given that: (games among men)−(games between men and women)=84\text{(games among men)} - \text{(games between men and women)} = 84(games among men)−(games between men and women)=84


  1. Number of games among the men

Number of pairs of men: (m2)\binom{m}{2}(2m​)

Since each pair plays 2 games, total games among men: 2(m2)=2⋅m(m−1)2=m(m−1)2\binom{m}{2} = 2\cdot \frac{m(m-1)}{2} = m(m-1)2(2m​)=2⋅2m(m−1)​=m(m−1)


  1. Number of games between men and women

Each of the mmm men plays with each of the 222 women.

So number of man-woman pairs: m⋅2=2mm\cdot 2 = 2mm⋅2=2m

Each such pair plays 2 games, so total games between men and women: 2(2m)=4m2(2m)=4m2(2m)=4m


  1. Use the given condition

m(m−1)−4m=84m(m-1) - 4m = 84m(m−1)−4m=84

Simplify: m2−m−4m=84m^2 - m - 4m = 84m2−m−4m=84 m2−5m=84m^2 - 5m = 84m2−5m=84 m2−5m−84=0m^2 - 5m - 84 = 0m2−5m−84=0

Factorize: m2−12m+7m−84=0m^2 - 12m + 7m - 84 = 0m2−12m+7m−84=0 m(m−12)+7(m−12)=0m(m-12) + 7(m-12)=0m(m−12)+7(m−12)=0 (m−12)(m+7)=0(m-12)(m+7)=0(m−12)(m+7)=0

So, m=12orm=−7m=12 \quad \text{or} \quad m=-7m=12orm=−7

Since number of men cannot be negative, m=12m=12m=12


  1. Check options
  • A: 121212 ✅
  • B: 999 ❌
  • C: 777 ❌
  • D: 111111 ❌

Hence the correct option is A.

PreviousNext

More from Permutations and Combinations

  • n − digit numbers are formed using only three digits 2, 5 and 7. The smallest value of n for which 900 such distinct numbers can be formed, is :2018 · MCQ
  • The number of four letter words that can be formed using the letters of the word BARRACK is :2018 · MCQ
  • 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 :2018 · MCQ
  • From 6 different novels and 3 different dictionaries, 4 novels and 1 dictionary are to be selected and arranged in a row on a shelf so that the dictionary is always in the middle. The number of such arrangements is :2018 · MCQ
  • If all the words, with or without meaning, are written using the letters of the word QUEEN and are arranged as in English dictionary, then the position of the word QUEEN is :2017 · MCQ
  • The number of ways in which 5 boys and 3 girls can be seated on a round table if a particular boy B1 and a particular girl G1 never sit adjacent to each other, is :2017 · MCQ
  • A man X has 7 friends, 4 of them are ladies and 3 are men. His wife Y also has 7 friends, 3 of them are ladies and 4 are men. Assume X and Y have no common friends. Then the total number of ways in which X and Y together can throw a party…2017 · MCQ
  • If the four letter words (need not be meaningful ) are to be formed using the letters from the word “MEDITERRANEAN” such that the first letter is R and the fourth letter is E, then the total number of all such words is :2016 · MCQ