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  • Question
  • In a two-digit number, the digit at the unit's place is 1 less than twice the digit at the ten's place. If the digits at unit's and ten's place are interchanged, the difference between the new and the original number is less than the original number by 20. The original number is


  • Options
  • A. 47
  • B. 59
  • C. 23
  • D. 35

  • Correct Answer
  • 47 

    Explanation

    let us assume the ten's digit number be x and unit's place digit be y.
    Then two digit Original Number = 10x + y
    According to question ? y = 2x - 1 ................(1)
    When digits are interchanged then new number = 10y + x
    If the digits at unit's and ten's place are interchanged, the difference between the new and the original number is less than the original number by 20,
    New Number - Original Number = Original number - 20
    ? 10y + x - (10x + y) = 10x + y - 20
    ? 10y + x - 10x - y - 10x - y = - 20
    ? 8y - 19x = - 20
    ? 19x - 8y = 20 ...................(2)
    Put the value of y from equation (1) in above equation (2).
    ? 19x - 8(2x - 1) = 20
    ? 19x - 16x - 8 = 20
    ? 7x = 20 + 8
    ? 7x = 28
    ? x = 28/7
    ? x = 4
    Put the value of y in equation (1)
    From (i) y = 2 x 4 -1 = y = 7
    ? original number = 10x + y =10 x 4 + 7 = 47.


  • More questions

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      The median for the data 2, 4, 6, 8, 10, 12, 14 is

    • Options
    • A. 6
    • B. 8
    • C. 9.5
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    • Discuss
    • 2. 
      The value of 47 / 10000 is?

    • Options
    • A. .0047
    • B. .0470
    • C. .00047
    • D. .000047
    • Discuss
    • 3. If 4x = 18y, then the value of ( x/y - 1) is

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    • A. 1 3
    • B. 7 2
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    • 4. 
      If the price of 23 toys is Rs. 276, then what will the price (Rs.) of 12 toys?

    • Options
    • A. 144
    • B. 158
    • C. 159
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    • 5. 
      .02 =(......?.....)%

    • Options
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    • 6. 
      If 36 men can do a piece of work in 25 hours, in how many hours will 15 men do it?

    • Options
    • A. 45
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    • 7. 
      2?63 / 11 =233

    • Options
    • A. 4
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    • D. 5
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    • 8. 
      When 121012 is divided by 12, the remainder is

    • Options
    • A. 0
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    • C. 3
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    • Discuss
    • 9. 
      Aarti can do a piece of work in 6 days. In how many days will she complete three time of work of same type?

    • Options
    • A. 18 days
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    • 10. 
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    • Options
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