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Question

If blank to the power of n P subscript 5 equals to the power of n P subscript 6  then n is :

  1. 15
  2. 7
  3. 6
  4. 10

Hint:

To find the value of n inblank to the power of n P subscript 5 equals to the power of n P subscript 6 we will first use the formula P with r below and n on top equals fraction numerator n factorial over denominator left parenthesis n minus r right parenthesis factorial end fraction then we will equate both side to get the value of n.

The correct answer is: 6


    Given, blank to the power of n P subscript 5 equals to the power of n P subscript 6
    rightwards double arrow fraction numerator n factorial over denominator open parentheses n minus 5 close parentheses factorial end fraction equals fraction numerator n factorial over denominator open parentheses n minus 6 close parentheses factorial end fraction
rightwards double arrow open parentheses n minus 6 close parentheses factorial equals open parentheses n minus 5 close parentheses factorial
rightwards double arrow open parentheses n minus 6 close parentheses factorial equals open parentheses n minus 5 close parentheses open parentheses n minus 6 close parentheses factorial
rightwards double arrow n minus 5 equals 1
rightwards double arrow n equals 1 plus 5
rightwards double arrow n equals 6

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