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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.


  • Linear Equation problems


    Search Results


    • 1. 
      11 friends went to a hotel and decided to pay the bill amount equally, But 10 of them could pay ? 60 each, as a result 11th has to pay ? 50 extra than his share . Find the amount paid by him?

    • Options
    • A. ?105
    • B. ?110
    • C. ?115
    • D. ?120
    • Discuss
    • 2. 
      A man ordered 4 pairs of black socks and some pairs of brown socks. The price of a black sock is double that of a brown pair. While preparing the bill the clerk interchanged the number of black and brown pairs by mistake which increased the bill by 50%. The ratio of the number of black and brown pairs of socks in the original order was :

    • Options
    • A. 2:1
    • B. 1:4
    • C. 1:2
    • D. 4:1
    • Discuss
    • 3. 
      The present ages of two persons are 36 and 50 years respectively, if after n years the ratio of their ages will be 3:4, then the value of n is

    • Options
    • A. 3
    • B. 4
    • C. 7
    • D. 6
    • Discuss
    • 4. 
      Bus fare between Rajpur and Mirpur for one Adult is six times the fare of one child. If an adult's bus fare is ?114/-, how much amount will be paid by 4 adults and 5 children together for travelling the same distance?

    • Options
    • A. ? 505/-
    • B. ? 551/-
    • C. ?572/-
    • D. ?560/-
    • Discuss
    • 5. 
      A man has ?480 in the denominations of 1 rupee notes , 5 rupee notes and 10 rupee notes. The number of notes of each denomination is equal. What is the total number of notes that he has

    • Options
    • A. 45
    • B. 60
    • C. 75
    • D. 90
    • Discuss
    • 6. 
      Which of the following equations is a quadratic?

    • Options
    • A. x3 - x2 - x + 5 = 0
    • B. x4 - 10
    • C. 7x2 = 49
    • D. x4 - x3 = 9000
    • Discuss
    • 7. 
      Which of the following equations has real roots?

    • Options
    • A. 2x2 - 3x + 4 = 0
    • B. (x - 1) (2x - 5) = 0
    • C. 3x2 + 4x + 5 = 0
    • D. Cannot be determined
    • Discuss
    • 8. 
      Find the roots of the equation 2x 2 - 9x - 18 = 0.

    • Options
    • A. 3/2 and 6
    • B. -3/2 and - 6
    • C. -3/2 and 6
    • D. 3/2 and -6
    • Discuss
    • 9. 
      If one root of x 2 - 6kx + 5 = 0 is 5, find the value of k.

    • Options
    • A. -1/2
    • B. -1
    • C. 1
    • D. 2
    • Discuss
    • 10. 
      Find the roots of the equation 2x 2 - 11x + 15 = 0

    • Options
    • A. 3 and 5/2
    • B. -3 and -5/2
    • C. 5 and 3/2
    • D. -5 and -3/2
    • Discuss


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