Number System


  1. A number divided by 13 leaves a remainder 1 and if the quotient, thus obtained, is divided by 5, we get a remainder of 3. What will be the remainder if the number is divided by 65 ?









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    Let the least number be x.

    Correct Option: D

    Let the least number be x.

    y = 5 × 1 + 3 = 8
    x = 13 × 8 + 1 = 105
    On dividing 105 by 65,
    ⇒ 105 = ( 65 × 1 ) + 40
    Hence required remainder = 40


  1. In a question on division, the divisor is 7 times the quotient and 3 times the remainder. If the remainder is 28, then the dividend is









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    Given , Remainder = 28
    Let the quotient be Q and the remainder be R. Then
    According to question ,
    Divisor = 7 Q = 3 R

    Correct Option: D

    Given , Remainder = 28
    Let the quotient be Q and the remainder be R. Then
    According to question ,
    Divisor = 7 Q = 3 R

    ∴  Q =
    3
    R =
    3
    × 28 = 12
    77

    ⇒ Quotient = 12
    ∴ Divisor = 7 Q = 7 × 12 = 84
    ∴ Dividend = Divisor × Quotient + Remainder = 84 × 12 + 28 = 1008 + 28 = 1036
    Hence the dividend is 1036.



  1. A number consists of two digits. If the number formed by interchanging the digits is added to the original number, the resulting number (i.e. the sum) must be divisible by









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    Let the number be 10a + b .
    After interchanging the digits, the number obtained = 10b + a.

    Correct Option: A

    Let the number be 10a + b .
    After interchanging the digits, the number obtained = 10b + a.
    According to the question,
    Resulting number = 10a + b + 10b + a
    Resulting number = 11a + 11b
    Resulting number = 11 (a + b)
    which is exactly divisible by 11.


  1. If two numbers are each divided by the same divisor, the remainders are respectively 3 and 4. If the sum of the two numbers be divided by the same divisor, the remainder is 2. The divisor is









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    Let two numbers are a and b and the divisor is d .
    According to question ,

    ∴  R1 =
    a
    = 3
    d

    ∴  R2 =
    b
    = 4
    d

    Correct Option: C

    Let two numbers are a and b and the divisor is d .
    According to question ,

    ∴  R1 =
    a
    = 3
    d

    ∴  R2 =
    b
    = 4
    d

    Now ,   R =
    3 + 4
    =
    3 + 4
    = 2
    dd

    ⇒ 7 - 2 = 5 is divisible by d .
    Required divisor = 5 { ∴ d > 4 }



  1. (719 + 2) is divided by 6, the remainder is :









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    Using the Binomial expansion , we have
    (x + 1)n = xn + nc1 xn–1 +
    nc2 xn– 2 + ..... + ncn–1 x +1
    Here, each term except the last term contains x. Obviously, each term except the last term is exactly divisible by x.

    Correct Option: B

    Using the Binomial expansion , we have
    (x + 1)n = xn + nc1 xn–1 +
    nc2 xn– 2 + ..... + ncn–1 x +1
    Here, each term except the last term contains x. Obviously, each term except the last term is exactly divisible by x.
    Following the same logic,
    ∴ 719 = (6 + 1)19 has each term except last term divisible by 6.
    Hence, 719 + 2 when divided by 6 leaves remainder
    ⇒ 719 + 2 = 1 + 2 = 3
    Hence the remainder is 3.