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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

    • 1. 
      A person sold an article for ? 3600 and got a profit of 20%. Had he sold the article for ? 3150, how much profit would he have got?

    • Options
    • A. 4%
    • B. 5%
    • C. 6%
    • D. 10%
    • Discuss
    • 2. 
      Two lots of onions with equal quantity, one costing ? 10 per kg and the other costing ? 15 per kg, are mixed together and whole lot is sold at ? 15 per kg. What is the profit or loss?

    • Options
    • A. 10% loss
    • B. 10% profit
    • C. 20% profit
    • D. 20% loss
    • Discuss
    • 3. 
      By selling 32 orange for ? 30 a man loses 25%. How many oranges should be sold for ? 24 so as to gain 20% in the transaction?

    • Options
    • A. 16
    • B. 24
    • C. 32
    • D. 28
    • Discuss
    • 4. 
      Kamlesh purchased 120 reams of paper at ? 100 per ream and the expenditure on transport was ? 480. He had to pay an octroi duty of 50 paise per ream and the coolie charges were ? 60. What should he charge per ream to gain 40%?

    • Options
    • A. ?155
    • B. ? 147
    • C. ? 138
    • D. ? 165
    • Discuss
    • 5. 
      A dishonest dealer sells his goods at 10% loss on cost price and uses 30% less weight. What is his profit or loss per cent?

    • Options
    • A. 284/7 % loss
    • B. 283/7 % gain
    • C. 283/7 % loss
    • D. 284/7 % gain
    • Discuss
    • 6. 
      A man sold two houses for ? 96000 each. In the sale of the first house, he incurred 20% profit and in the sale of the second, he incurred 20% loss. what is the gain or loss percentage in total?

    • Options
    • A. 6% gain
    • B. 6% loss
    • C. 4% gain
    • D. 4% loss
    • Discuss
    • 7. 
      A man sold two watches, each for ? 495. If he gained 10% on one watch and suffered a loss of 10% on the other, then what is the loss of gain percentage in the transaction?

    • Options
    • A. 1 % gain
    • B. 1% loss
    • C. 100/99% loss
    • D. Neither gain nor loss
    • Discuss
    • 8. 
      A person sold an article for ? 136 and got 15% loss, had he sold it for ? N, he would have got a profit of 15%. Which one of the following is correct?

    • Options
    • A. 190 < N < 200
    • B. 180 < N < 190
    • C. 170 < N < 180
    • D. 160 < N < 170
    • Discuss
    • 9. 
      A Seller uses 920g in place of one kg to sell his goods. When he sells his article at 15% gain on cost price, the actual percentage of profit is?

    • Options
    • A. 20%
    • B. 15%
    • C. 25%
    • D. 30%
    • Discuss
    • 10. 
      A shopkeeper sells transistors at 15% above its cost price. If he had bought it at 5% more than what he paid for it and sold it for ? 6 more, he would have gained 10%. The cost price of the transistor is?

    • Options
    • A. ? 800
    • B. ? 1000
    • C. ? 1200
    • D. ? 1400
    • Discuss


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