Mathematics The sum of digits of a two-digit number is 7. If the digits are reversed and the resulting number is decreased by 2, twice of the original number is obtained. Find the original numberClass: 10

 The sum of digits of a two-digit number is 7. If the digits are reversed and the resulting number is decreased by 2, twice of the original number is obtained. Find the original number


Class: 10


  1. A
      27
  2. B
      29
  3. C
      25
  4. D
      20  

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    Solution:

     Let the unit place = x of the number
     Let the tenth place of the number = y
     Number = 10y + x
     x + y = 7   ________(i)
     Reversed number = 10x + y
     According to question
      (10x + y) 2 = 2(10y + x)
      10x + y 2 = 20y + 2x
     8x 19y = 2  _______(ii)
     From eqn (i) & eqn (ii)
     x + y = 7 19
     8x 19y = 2
     27x = 135
     n = 5
     Put in eqn (i)
     x + y = 7
     5 + y = 7
    y = 2
     Number = 10y + x
    = 10 2 + 5 = 25
      
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