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Friday, 9 October

JEE Main 2024 · MathsMultiple choiceSingle correctMediumCalculation

JEE Main 6 April 2024, Shift 2, Maths Q6

Question 6 of 90 in this shift, Maths question 6 of 30, Section A.

Let 0≤r≤n0\le r\le n. If n+1Cr+1:nCr:n−1Cr−1=55:35:21^{n+1}C_{r+1}:{}^{n}C_r:{}^{n-1}C_{r-1}=55:35:21, then 2n+5r2n+5r is equal to :
  1. (1)50Official answer
  2. (2)55
  3. (3)60
  4. (4)62

Official answer

Option 1

NTA final key.

Chapter
Permutations and Combinations
Topic
Permutations and Combinations
Idea tested
Pascal's Rule and nCr Properties

Same idea in other shifts

Asked 2× in all
  1. 31 Jan 2024, Shift 2 · Q6If for some m,nm,n; 6Cm+2(6Cm+1)+6Cm+2>8C3{}^6C_m+2\left({}^6C_{m+1}\right)+{}^6C_{m+2}>{}^8C_3 and n−1P3:nP4=1:8{}^{n-1}P_3:{}^nP_4=1:8, then nPm+1+n+1Cm{}^nP_{m+1}+{}^{n+1}C_m…MediumSingle correct

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 42 of the 174 JEE Main shifts held from 2017 to 2026.