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JEE Main & Advanced JEE Main Paper (Held On 9 April 2014)

  • question_answer
    The sum of the digits in the unit's place of all the 4-digitnumbers formed by using the numbers 3, 4, 5 and 6, without repetition, is:   [JEE Main Online Paper ( Held On 09 Apirl  2014  )

    A) 432                        

    B) 108

    C) 36                                          

    D) 18

    Correct Answer: B

    Solution :

    With 3 at unit place, total possible four digit number (without repetition) will be 3 ! = 6 With 4 at unit place, total possible four digit numbers will be 3! = 6 With 5 at unit place, total possible four digit numbers will be 3! = 6 With 6 at unit place, total possible four digit numbers will be 3! = 6 Sum of unit digits of all possible numbers \[=6\times 3+6\times 4+6\times 5+6\times 6\] \[=6[3+4+5+6]\] = 6 [18] = 108


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