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    • Question

      When the digits of a two-digit number are interchanged,

      the new number becomes 5 less than 150% of the original number. If the sum of the digits is 10, find the original number.
      A 64 Correct Answer Incorrect Answer
      B 46 Correct Answer Incorrect Answer
      C 56 Correct Answer Incorrect Answer
      D 73 Correct Answer Incorrect Answer

      Solution

      Let the unit digit and tens digit of the original number be ‘y’ and ‘x’, respectively.
      Original number = (10x + y)

      According to the data given: 
      10y + x = 1.5 × (10x + y) − 5

      Multiplying both sides by 2, 
      20y + 2x = 30x + 3y − 10 
      ⇒ 28x − 17y = 10  …. (I)

      And, x + y = 10  …. (II)

      From (II), x = 10 − y. Substitute in (I): 
      28(10 − y) − 17y = 10 
      280 − 45y = 10 
      45y = 270 
      y = 6

      Then x = 10 − 6 = 4. 
      So, original number = (10×4 + 6) = 46.

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