Maths-
General
Easy

Question

If scriptbase P subscript 7 end scriptbase presuperscript n equals 42 times to the power of n P subscript 5 then n is :

  1. 5
  2. 7
  3. 12
  4. 9

Hint:

In the question we will use the formulablank to the power of n P subscript r equals fraction numerator n factorial over denominator open parentheses n minus r close parentheses factorial end fraction on both sides then we will simplify to get the value of n.

The correct answer is: 12


    Given, scriptbase P subscript 7 end scriptbase presuperscript n equals 42 times to the power of n P subscript 5
    rightwards double arrow fraction numerator n factorial over denominator open parentheses n minus 7 close parentheses factorial end fraction equals 42. fraction numerator n factorial over denominator open parentheses n minus 5 close parentheses factorial end fraction
rightwards double arrow fraction numerator open parentheses n minus 5 close parentheses factorial over denominator open parentheses n minus 7 close parentheses factorial end fraction equals 42
rightwards double arrow fraction numerator open parentheses n minus 5 close parentheses open parentheses n minus 6 close parentheses open parentheses n minus 7 close parentheses factorial over denominator open parentheses n minus 7 factorial close parentheses end fraction equals 42
rightwards double arrow open parentheses n minus 5 close parentheses open parentheses n minus 6 close parentheses equals 7 cross times 6
rightwards double arrow open parentheses 12 minus 5 close parentheses open parentheses 12 minus 6 close parentheses equals 7 cross times 6
rightwards double arrow n equals 12

    Book A Free Demo

    +91

    Grade*

    Related Questions to study