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    • Question

      A two-digit number decreases by 54 when its digits are

      reversed. If the sum of its digits is 10, what is the original number?
      A 17 Correct Answer Incorrect Answer
      B 71 Correct Answer Incorrect Answer
      C 82 Correct Answer Incorrect Answer
      D 28 Correct Answer Incorrect Answer

      Solution

      For the original number, let the unit digit and ten’s digit be ‘y’ and ‘x’, respectively.

      So, the original number = (10x + y)

      Now, if the digits are reversed, the new number = (10y + x).

      ATQ, (10x + y) – (10y + x) = 54

      Or, 9x – 9y = 54

      So, x – y = 6……….(i)

      And, given that, x + y = 10………(ii)

      By adding equation (i) and equation (ii), we get,

      2x = 16

      So, ‘x’ = 8

      And, ‘y’ = 2

      So, the original number = 10x + y = 10 × 8 + 2 = 80 + 2 = 82

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