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Permutations and Combinations

JEE Main 2024 (Online) 27th January Morning ShiftMCQMedium📈 Topic in 34% papers+4−1
Ques. 1JEE Main 2024, 27 January (Morning Shift)

n-1Cr= (k2-8 )nCr+1 if and only if :

  1. 2 2<k<2 3
  2. 2 2<k 3
  3. 2 3<k<3 3
  4. 2 3<k 3 2

Answer

(2) 2 2<k 3

Solution

nCr+1= nr+1 n-1Cr k2-8= n-1CrnCr+1= r+1n

0 r n-1 0< r+1n 1

8<k2 9 2 2<|k| 3

k [-3,-2 2) (2 2,3]

Of the options, only 2 2<k 3 fits.

Answer: (2)

Keep practising — Permutations and Combinations

Ques. 2JEE Main 2024, 27 January (Evening Shift)

Let = (4!)!(4!)3! and = (5!)!(5!)4!. Then :

  1. and
  2. and
  3. and
  4. and

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