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    Question

    The digits of a two-digit number ‘N’ are reversed to

    form a new number ‘M’. If M < N and N – M = 63, then which of the following maybe ‘N’?
    A 51 Correct Answer Incorrect Answer
    B 31 Correct Answer Incorrect Answer
    C 61 Correct Answer Incorrect Answer
    D 81 Correct Answer Incorrect Answer

    Solution

    ATQ; Let the original number = N = ‘10a + b’ So, the new number = M = ‘10b + a’ ATQ; N = M + 63 So, 10a + b = 10b – a + 63 Or, 9a – 9b = 63 Or, a – b = 7 So, possible pairs of ‘a’ and ‘b’ = (9, 2), (8, 1) So, possible values of ‘N’ = 92, 81 Alternate Solution From option ‘a’: N = 29 So, M = 92 Since, M > N {not possible} N = 81 So, M = 18 Also, N – M = 81 – 18 = 63

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