Number System


  1. What decimal of a week is an hour ?









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    Required answer

    =
    1
    =
    1
    = 0.0059
    7 × 24168

    Correct Option: A

    Required answer

    =
    1
    =
    1
    = 0.0059
    7 × 24168


  1. In an exam the sum of the scores of A and B is 120, that of B and C is 130 and that of C and A is 140. Then the score of C is :









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    A + B = 120
    B + C = 130
    C + A = 140
    On adding,
    2 (A + B + C) = 120 + 130 + 140 = 390

    ⇒  A + B + C =
    390
    = 195
    2

    ∴  Marks obtained by C = Marks
    obtained by (A + B + C) – Marks
    obtained by (A + B)
    = 195 – 120 = 75

    Correct Option: B

    A + B = 120
    B + C = 130
    C + A = 140
    On adding,
    2 (A + B + C) = 120 + 130 + 140 = 390

    ⇒  A + B + C =
    390
    = 195
    2

    ∴  Marks obtained by C = Marks
    obtained by (A + B + C) – Marks
    obtained by (A + B)
    = 195 – 120 = 75



  1. If p = – 0.12, q = –0.01 and r = – 0.015, then the correct relationship among the three is :









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    0.01 < 0.015 < 0.12
    ⇒  – 0.01 > – 0.015 > – 0.12
    ⇒  p < r < q

    Correct Option: D

    0.01 < 0.015 < 0.12
    ⇒  – 0.01 > – 0.015 > – 0.12
    ⇒  p < r < q


  1. Among the following statements, the statement which is not correct is :









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    Every rational number is a real number.

    Correct Option: C

    Every rational number is a real number.



  1. If a certain number of two digits is divided by the sum of its digits, the quotient is 6 and the remainder is 3. If the digits are reversed and the resulting number is divided by the sum of the digits, the quotient is 4 and the remainder is 9. The sum of the digits of the number is









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    Let the number be 10x + y.
    Dividend = Divisor × quotient + remainder
    ∴  10x + y = 6(x + y) + 3
    ⇒  10x + y = 6x + 6y + 3
    ⇒  10x – 6x + y – 6y = 3
    ⇒  4x – 5y = 3     ....(i)
    Again, 10y + x = 4 (x + y) + 9
    ⇒  10y + x = 4x + 4y + 9
    ⇒  6y – 3x = 9
    ⇒  2y – x = 3     ....(ii)
    ∴  By equation (i) + 4 × (ii),


    4x – 5y = 3
    8y – 4x = 12
    ____________
    3y = 15
    ⇒y = 5

    From equation (ii),
    2 × 5 – x = 3 ⇒  x = 10 – 3 = 7
    ∴  Sum of digits = x + y = 7 + 5 =12

    Correct Option: C

    Let the number be 10x + y.
    Dividend = Divisor × quotient + remainder
    ∴  10x + y = 6(x + y) + 3
    ⇒  10x + y = 6x + 6y + 3
    ⇒  10x – 6x + y – 6y = 3
    ⇒  4x – 5y = 3     ....(i)
    Again, 10y + x = 4 (x + y) + 9
    ⇒  10y + x = 4x + 4y + 9
    ⇒  6y – 3x = 9
    ⇒  2y – x = 3     ....(ii)
    ∴  By equation (i) + 4 × (ii),


    4x – 5y = 3
    8y – 4x = 12
    ____________
    3y = 15
    ⇒y = 5

    From equation (ii),
    2 × 5 – x = 3 ⇒  x = 10 – 3 = 7
    ∴  Sum of digits = x + y = 7 + 5 =12