Number System


  1. The number of integers in between 100 and 600, which are divisible by 4 and 6 both, is









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    We have to find such numbers which are divisible by 12 (LCM of 4 and 6).
    Number of numbers divisible by 12 and lying between 1 to 600

    =
    600
    −1 = 49
    12

    Number of numbers divisible by 12 from 1 to 100 =
    100
    = 8
    12

    Correct Option: C

    We have to find such numbers which are divisible by 12 (LCM of 4 and 6).
    Number of numbers divisible by 12 and lying between 1 to 600

    =
    600
    −1 = 49
    12

    Number of numbers divisible by 12 from 1 to 100 =
    100
    = 8
    12

    ∴ Required answer = 49 – 8 = 41


  1. The value of λ for which the expression x3 + x2 – 5x + λ will be divisible by (x – 2) is :









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    (x – 2) is a factor of polynomial P (x) = x3 + x2 – 5x + λ.
    ∴  P(2) = 0 (on putting x = 2)

    Correct Option: B

    (x – 2) is a factor of polynomial P (x) = x3 + x2 – 5x + λ.
    ∴  P(2) = 0 (on putting x = 2)
    ⇒  23 + 22 – 5 × 2 + λ = 0
    ⇒  8 + 4 – 10 + λ = 0
    ⇒  λ + 2 = 0
    ∴  λ = - 2



  1. If the number formed by the last two digits of a three digit integer is an integral multiple of 6, the original integer itself will always be divisible by









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    According to question ,
    Required Number = 100p + 10q + r
    ∵  10q + r = 6m
    ∴  Number = 100x + 6m, where m is a positive integer.

    Correct Option: C

    According to question ,
    Required Number = 100p + 10q + r
    ∵  10q + r = 6m
    ∴  Number = 100x + 6m, where m is a positive integer.
    Number = 2 (50p + 3m)
    Hence required answer is 2 .


  1. How many numbers between 400 and 800 are divisible by 4, 5 and 6 ?









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    LCM of 4, 5 and 6 = 60
    Quotient on dividing 800 by 60 = 13
    Quotient on dividing 400 by 60 = 6
    ∴  Required answer = Quotient on dividing 800 by 60 – Quotient on dividing 400 by 60

    Correct Option: A

    LCM of 4, 5 and 6 = 60
    Quotient on dividing 800 by 60 = 13
    Quotient on dividing 400 by 60 = 6
    ∴  Required answer = Quotient on dividing 800 by 60 – Quotient on dividing 400 by 60
    ∴  Required answer = 13 – 6 = 7
    2nd Method to solve this question :
    First number greater than 400
    that is divisible by 60 = 420
    Smaller number than 800 that
    is divisible by 60 = 780
    It is an Arithmetic Progression with common difference = 60
    By tn = a + (n – 1)d
    780 = 420 + (n – 1) × 60
    ⇒ (n – 1) × 60 = 780 – 420 = 360
    ⇒ (n – 1) = 360 ÷ 60 = 6
    ⇒ n = 6 + 1 = 7



  1. A number x when divided by 289 leaves 18 as the remainder. The same number when divided by 17 leaves y as a remainder. The value of y is









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    Here, the first divisor (289) is a multiple of second divisor (17).
    ∴ Required remainder = Remainder obtained on dividing 18 by 17

    Correct Option: D

    Here, the first divisor (289) is a multiple of second divisor (17).
    ∴ Required remainder = Remainder obtained on dividing 18 by 17 = 1
    Therefore required answer is 1.