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

2025 · 3 Apr · 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. /2025 · 3 Apr · Shift 2 · Q27

Permutations and Combinations question

2025 · 3 Apr · Shift 2 · Q27

JEE MainMathematicsPermutations and CombinationsMCQ+4 / −1
Line L1L_1L1​ of slope 2 and line L2L_2L2​ of slope 12\frac{1}{2}21​ intersect at the origin O . In the first quadrant, P1\mathrm{P}_1P1​, P2,…,P12P_2, \ldots, P_{12}P2​,…,P12​ are 12 points on line L1L_1L1​ and Q1,Q2,…,Q9Q_1, Q_2, \ldots, Q_9Q1​,Q2​,…,Q9​ are 9 points on line L2L_2L2​. Then the total number of triangles, that can be formed having vertices at three of the 22 points O,P1,P2,…,P12\mathrm{O}, \mathrm{P}_1, \mathrm{P}_2, \ldots, \mathrm{P}_{12}O,P1​,P2​,…,P12​, Q1,Q2,…,Q9\mathrm{Q}_1, \mathrm{Q}_2, \ldots, \mathrm{Q}_9Q1​,Q2​,…,Q9​, is:
  1. A
    1026
  2. B
    1188
  3. C
    1134
  4. D
    1080
View written solutionFree

Correct answer: C

  1. Count total points

There are:

  • 1 point at the origin OOO
  • 12 points P1,P2,…,P12P_1, P_2, \dots, P_{12}P1​,P2​,…,P12​ on line L1L_1L1​
  • 9 points Q1,Q2,…,Q9Q_1, Q_2, \dots, Q_9Q1​,Q2​,…,Q9​ on line L2L_2L2​

So total number of points is 1+12+9=22.1+12+9=22.1+12+9=22.

If no three points were collinear, the number of triangles would be (223)=22⋅21⋅206=1540.\binom{22}{3} = \frac{22\cdot 21\cdot 20}{6}=1540.(322​)=622⋅21⋅20​=1540.

  1. Subtract collinear triples

A triangle cannot be formed if all 3 chosen points are collinear.

The only collinear sets of 3 or more points lie on the two given lines.

On line L1L_1L1​

Points on L1L_1L1​ are: O,P1,P2,…,P12O, P_1, P_2, \dots, P_{12}O,P1​,P2​,…,P12​ So there are 131313 points on L1L_1L1​.

Number of ways to choose 3 collinear points from these is (133)=13⋅12⋅116=286.\binom{13}{3} = \frac{13\cdot 12\cdot 11}{6}=286.(313​)=613⋅12⋅11​=286.

On line L2L_2L2​

Points on L2L_2L2​ are: O,Q1,Q2,…,Q9O, Q_1, Q_2, \dots, Q_9O,Q1​,Q2​,…,Q9​ So there are 101010 points on L2L_2L2​.

Number of ways to choose 3 collinear points from these is (103)=10⋅9⋅86=120.\binom{10}{3} = \frac{10\cdot 9\cdot 8}{6}=120.(310​)=610⋅9⋅8​=120.

  1. Compute number of triangles

Hence total number of triangles is (223)−(133)−(103)\binom{22}{3}-\binom{13}{3}-\binom{10}{3}(322​)−(313​)−(310​) =1540−286−120=1134.=1540-286-120=1134.=1540−286−120=1134.

  1. Check options

113411341134 corresponds to Option C.

Therefore, the correct answer is 1134.\boxed{1134}.1134​.

PreviousNext

More from Permutations and Combinations

  • Let m and n,(m<n), be two 2-digit numbers. Then the total numbers of pairs (m,n), such that gcd(m,n)=6, is ​ .2025 · Numerical
  • From a group of 7 batsmen and 6 bowlers, 10 players are to be chosen for a team, which should include atleast 4 batsmen and atleast 4 bowlers. One batsmen and one bowler who are captain and vice-captain respectively of the team should be…2025 · MCQ
  • There are 12 points in a plane, no three of which are in the same straight line, except 5 points which are collinear. Then the total number of triangles that can be formed with the vertices at any three of these 12 points is2025 · MCQ
  • From all the English alphabets, five letters are chosen and are arranged in alphabetical order. The total number of ways, in which the middle letter is ' M ', is :2025 · MCQ
  • In a group of 3 girls and 4 boys, there are two boys B1​ and B2​. The number of ways, in which these girls and boys can stand in a queue such that all the girls stand together, all the boys stand together, but B1​ and B2​ are not…2025 · MCQ
  • The number of words, which can be formed using all the letters of the word "DAUGHTER", so that all the vowels never come together, is :2025 · MCQ
  • The number of ways, 5 boys and 4 girls can sit in a row so that either all the boys sit together or no two boys sit together, is ​.2025 · Numerical
  • The number of 3 -digit numbers, that are divisible by 2 and 3 , but not divisible by 4 and 9 , is ​.2025 · Numerical