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Aptitude Questions : Number System

 

  • In a three digit number the digit in the unit’s place is twice the digit in the ten’s place and 1.5 times the digit in the hundred’s place. If the sum of all the three digits of the number is 13, what is the number?
    A. 356
    B. 456
    C. 436
    D. 626
    E. 516

    Answer & Explanation
    Answer – C. 436
    Explanation :
    100a + 10b + c
    c = 2b –> b = c/2
    c = 1.5a —> a = c/1.5
    c/1.5 + c/2 + c = 13
    6.5c = 39
    c = 6, b = 3, a = 4 => 436
  • In a two digit positive number, the digit at the units place is equal to the square of the digit in ten’s place and the difference between the number and the number obtained by interchanging the digits is 54. What is 40% of the original number?
    A. 15.6
    B. 37.2
    C. 39.4
    D. 24.8
    E. None of the Above

    Answer & Explanation
    Answer – A. 15.6
    Explanation :
    Let the number be 10x + y
    And y = x²
    10x + y – (10y + x) = 54
    9x – 9y = 54
    x – y = 6
    x²- x + 6 = 0
    x = 2, 3
    y = 4, 9
    So the no is 39
    39*40/100 = 15.6
  • If the positions of the digits of a two digit number are interchanged, the number obtained is smaller than the original number by 27. If the digits of the number are in the ratio of 1:2, what is the original number?
    A. 16
    B. 32
    C. 63
    D. 48
    E. Can not be determined

    Answer & Explanation
    Answer – C. 63
    Explanation :
    original number – 10x + y
    (10x + y) – (10y + x) = 27
    9(x – y) = 27
    x – y = 3
    y/x = 1/2
    x = 2y
    y = 3, x = 6 –>63
  • A certain number of two digits is three times the sum of its digits. If 45 is added to it, the digits are reversed. The number is _______
    A. 16
    B. 72
    C. 63
    D. 27
    E. Can not be determined

    Answer & Explanation
    Answer – D. 27
    Explanation :
    A certain number of two digits is three times the sum of its digits
    only 27 satisfies this condition.
    27 + 45 = 72
    Therefore Ans is – 27
  • The number obtained by interchanging the two digits of a two digit number is less than the original number by 27. If the difference between the two digits of the number is 3, then what is the original number?
    A. 64
    B. 72
    C. 65
    D. 73
    E. None of the Above

    Answer & Explanation
    Answer – E. None of the Above
    Explanation :
    original number – 10x + y
    (10x + y) – (10y + x) = 27
    9(x – y) = 27
    x – y = 3
    All the given options not follow the condition.
  • Two numbers such that the sum of twice the first number and thrice the second number is 100 and the sum of thrice the first number and twice the second number is 120. Which is larger number?
    A. 64
    B. 72
    C. 65
    D. 32
    E. None of the Above

    Answer & Explanation
    Answer – D. 32
    Explanation :
    2x + 3y = 100 –(i)
    3x + 2y = 120 –(ii)
    By Solving eqn (i) and (ii)
    x = 32, y = 12
  • The sum of two even numbers is six more than twice of the smaller number. If the difference between these two numbers is 6, If the larger number lies between 15 to 25 Which is the smaller number?
    A. 16
    B. 6
    C. 24
    D. 12
    E. Can not be determined

    Answer & Explanation
    Answer – D. 12
    Explanation :
    If 12 is smaller number then larger number is 18
    Sum =(12+18)=30
    Twice of the smaller number = 24.
    The sum of two even numbers is six more than twice of the smaller number. Therefore Number 12 satisfy both the conditions.
  • A number is divided by 2, 3, 4, 5 or 6, reminder in each case is one. But the number is exactly divisible by 7. The number lies between 250 and 350, the sum of digits of the number will be
    A. 4
    B. 7
    C. 6
    D. 10
    E. Can not be determined

    Answer & Explanation
    Answer – A. 4
    Explanation :
    LCM of 2, 3, 4, 5 and 6 is 60
    60 * 5 + 1 = 7x
    7x = 301
    Number – 301 ; The sum of digits of the number = 4
  • Sum of three consecutive odd numbers & three consecutive even numbers together is 231. Difference between the smallest odd number and the smallest even number is 11. What is the sum of the largest even number and largest odd number?
    A. 71
    B. 91
    C. 101
    D. 81
    E. Can not be determined

    Answer & Explanation
    Answer – D. 81
    Explanation :
    odd numbers – x-2, x, x+2 ; even numbers – y-2, y, y+2
    3x + 3y = 231
    x + y = 77
    (y – 2) – (x – 2) = 11
    y – x = 11
    x = 33, y = 44
    sum of the largest even number and odd number = 46 + 35 = 81
  • Sum of eight consecutive odd numbers is 656. Average of four consecutive even numbers is 87. What is the sum of the largest even number and largest odd number?
    A. 171
    B. 191
    C. 101
    D. 181
    E. 179

    Answer & Explanation
    Answer – E. 179
    Explanation :
    odd numbers — x-8, x-6, x-4, x-2, x, x+2, x+4, x+6
    x-8 + x-6 + x-4 + x-2 + x + x+2 + x+4 + x+6 = 656
    8x – 8 =656
    x = 83
    Even numbers — y-2, y, y+2, y+4
    4y + 4 = 87 * 4
    y = 86
    sum of the largest even number and odd number = 89 + 90 = 179

 

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