Maths-
General
Easy

Question

The number of ways in which 20 persons can sit on 8 chairs round a circular table is-

  1. 20P8    
  2. 19P8    
  3. 1/8(20P8)    
  4. None of these    

Hint:

Use formula
P presuperscript n subscript r space equals space fraction numerator n factorial over denominator left parenthesis n minus r right parenthesis factorial end fraction

C presuperscript n subscript r space equals space fraction numerator n factorial over denominator r factorial left parenthesis n minus r right parenthesis factorial end fraction

The correct answer is: 1/8(20P8)


    20 persons on 8 chairs (selecting 8 persons out of 20) = C presuperscript 20 subscript 8
    Nothespersons cabarrangei(81)7ways
    The number of ways in which 20 persons can sit on 8 chairs round a circular table is- C presuperscript 20 subscript 8 cross times 7!
    rightwards double arrow fraction numerator 20 factorial over denominator 8 factorial space cross times 12 factorial end fraction space cross times 7 factorial
rightwards double arrow space fraction numerator 20 factorial over denominator 12 factorial end fraction space space c a n space b e space w r i t t e n space a s space space P presuperscript 20 subscript 8 space left parenthesis P presuperscript n subscript r space equals space fraction numerator n factorial over denominator left parenthesis n minus r right parenthesis factorial end fraction right parenthesis
rightwards double arrow left parenthesis P presuperscript 20 subscript 8 space right parenthesis 1 over 8

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