Number System


  1. The last digit of the number obtained by multiplying the numbers 41 x 42 x 43 x 44 x 45 x 46 x 47 x 48 x 49 will be ?
    1. 0
    2. 1
    3. 4
    4. 5

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    Last digit will be multiplication of 1 x 2 x 3 x 4 x 5 x 6 x 7 x 8 x 9.
    It includes 5 & 2.

    Correct Option: A

    Last digit will be multiplication of 1 x 2 x 3 x 4 x 5 x 6 x 7 x 8 x 9.
    It includes 5 & 2.
    So, 5 x 2=10,
    0 will be the last digit.


  1. The sum of the digits of a two digit number is 10, when the number is reversed, the number increases by 72.Find the number.
    1. 64
    2. 82
    3. 19
    4. 37

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    Go through the options.

    Correct Option: C

    By checking options
    91-19=72

    Or

    Let the number be xy
    So 10x + y = 10 ..... (i)

    When the number is reversed the new number is yx
    So (10y + 10 ) - ( 10x +y ) = 72 ....(ii)

    From Eqs. (i) & (ii)
    x = 1 and y =9
    ∴number = 19



  1. Find the product of place value and face value of 5 in 65231
    1. 28000
    2. 25000
    3. 27000
    4. 26000

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    Place value of 5 in 65231 = 5 x 1000
    Face value = 5

    Correct Option: B

    Place value of 5 in 65231 = 5 x 1000
    = 5000

    Face value = 5

    required product = 5000 x 5 = 25000


  1. The units digit in the product ( 784 x 618 x 917 x 463 ) is
    1. 2
    2. 3
    3. 4
    4. 5

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    Units digit in the given product = Units digit of 4 x 8 x 7 x 3

    Correct Option: A

    Units digit in the given product = Units digit of 4 x 8 x 7 x 3
    = Units digit of 672
    = 2



  1. If 1x5x01 is divisible by 11, then the value of x is
    1. 6
    2. 4
    3. 8
    4. 9

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    N/A

    Correct Option: C

    When a number is divisible by 11, then sum of numbers at even place - sum of numbers at odd place = 0 or divisible by 11.

    ( x + x + 1 ) - ( 1+ 5 + 0 ) = 11
    ⇒ 2x - 5 = 11
    ∴ x = 8