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Question

A set of (2n + 1) elements is given. The no. of subsets of the set which contain atmost n elements -

  1. 2n    
  2. 2n+1    
  3. 2n –1    
  4. 22n    

The correct answer is: 22n


    No. of subsets
    = 2n+1C0 + 2n+1C1 + 2n+1C2 +...........+ 2n+1Cn = N
    (let) We have 2N = 2n+1C0 + 2n+1C1 .................2n+1C2n +1
    2N = 22n + 1
    N = 22n

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