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  • Question
  • In a two digit positive number the unit digit is equal to the square of ten's place digit. The difference between the original number and the number formed by interchanging the digit is 54. What of 40% of the original number?


  • Options
  • A. 64
  • B. 73
  • C. 84
  • D. Couldn't be determined

  • Correct Answer
  •  

    Explanation

    Let ten's place digit be a and unit's place digit be a2
    Original number = 10 x a + 1 x a2 = 10a + a2
    The number formed by interchanging the digits,
    New number = 10 x a 2 + 1 x a = 10a 2 + a
    According to the question
    (10a2 + a) - ( 10a + a2) = 54
    ? 10a2 + a - 10a - a 2 = 54
    ? 9a2 - 9a = 54
    ? 9( a2 - a) = 54
    ? ( a2 - a) = 54/9
    ? ( a2 - a) = 6
    ? a2 - a - 6 = 0
    ? a2 - 3a + 2a - 6 = 0
    ? a (a - 3) + 2 (a - 3) = 0
    ? (a - 3) (a + 2) = 0
    ? a = 3, - 2
    ? Ten,s digit = a = 3
    Unit's digit = a2 = 32 = 9
    Original number = 39
    ? Required number = 39 x 40/100 = 15.6


  • Number System problems


    Search Results


    • 1. 
      In a three-digit number, the digit in the unit's place is four times the digit in the hundred's place. If the digit in the unit's place and the ten's places are interchanged, the new number so formed is 18 more than the original number. If the digit in the hundred's place is one third of the digit in the ten's place, then what is 25% of the original number?

    • Options
    • A. 67
    • B. 84
    • C. 137
    • D. Couldn't not be determined
    • Discuss
    • 2. 
      In an examination paper of five questions 5% of the candidates answered all of them and 5% answered none. Of the rest 25% candidates answered only one question and 20% answered 4 question. If 396 candidates answered either 2 question or 3 question. The number of candidates that appeared for the examination was

    • Options
    • A. 800
    • B. 1000
    • C. 850
    • D. 900
    • Discuss
    • 3. 
      X, Y and Z had have dinner together. The cost of the meal of Z was 20% more then that of Y and the cost of the meal of X was 5/6 as much as the cost of the meal of Z. If Y paid ? 100, then what was the total amount that all the three of them had paid?

    • Options
    • A. ? 285
    • B. ? 300
    • C. ? 335
    • D. None of these
    • Discuss
    • 4. 
      The taxi charges in a city contain fixed charges and additional charge per kilometer. The fixed charge is for a distance of up to 5 km and additional charge per kilometer thereafter. The charge for a distance of 10 km is ? 350 and for 25 km is ? 800. The charge for a distance of 30 km is

    • Options
    • A. ? 800
    • B. ? 750
    • C. ? 900
    • D. ? 950
    • Discuss
    • 5. 
      There are 200 question in a 3 hour examination. Among 200 question, 50 are Mathematics, 100 are from GK and 50 are from Sciences. Ram spent twice as much time on each Mathematics question for each other question. How many minute did he spend on Mathematics questions?

    • Options
    • A. 36
    • B. 72
    • C. 100
    • D. 60
    • Discuss
    • 6. 
      Find the maximum number of trees which can be planted 20 m apart on the two sides of a straight road 1760 m long.

    • Options
    • A. 174
    • B. 176
    • C. 180
    • D. 178
    • Discuss
    • 7. 
      When 1/7 of a number is subtracted from the number itself, it gives the same value as the sum of all the angels of a triangle. What is the number?

    • Options
    • A. 224
    • B. 210
    • C. 140
    • D. 350
    • Discuss
    • 8. 
      In a division sum, the divisor is ten times the quotient and five times the remainder. If the remainder is 46, then find the dividend?

    • Options
    • A. 5388
    • B. 5343
    • C. 5336
    • D. 5391
    • Discuss
    • 9. 
      The product of two consecutive odd number is 6723. What is the greater number?

    • Options
    • A. 89
    • B. 85
    • C. 91
    • D. 83
    • Discuss
    • 10. 
      The sum of the four consecutive even numbers is 284. What would be the smallest number.

    • Options
    • A. 72
    • B. 74
    • C. 68
    • D. 66
    • Discuss


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