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Railways R.R.C. (Kolkata) Solved Paper Held on 2nd Shift 27-10-2013

  • question_answer
    A two-digit number is three times the sum of its digits. If 45 is added to the number, its digits are interchanged. The sum of the digits of the number is?

    A) 5                                 

    B) 7

    C) 9                     

    D) None of these

    Correct Answer: C

    Solution :

    Let the two digit number is \[(10x+y)\] As per question? \[10x+y=3(x+y)\] \[=3x+3y\] \[7x=2y\] \[x=\frac{2}{7}\,\,y\]                 ? (1)                                            Again from question? \[10x+y+45=10y+x\] \[9x+45=9y\] \[9\,\,(y-x)=45\] \[y-x=5\] \[y-\frac{2}{7}y=5\]      [From equation (1)] \[5y=7\times 5\] \[y=7\,\,and\,\,x=2\] \[\therefore \text{Required}\,\,sum\,\,of\,\,digits=x+y\]                                         \[=7+2=9\]


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