Number System Questions and Answers : Quantitative Aptitude

  • Formulas:-


  • 0, 1, 2, 3, ----9. are called digits.


  • 10, 11, 12,----- are called Number.


  • Natural number (N) :- Counting numbers are called natural numbers.

    Example:- 1, 2, 3,---etc. are all natural numbers. minimum natural number 1 and maximum natural

    number ∞


  • Whole numbers (W) :- All counting numbers together with zero from the set of whole numbers

    Example:- 0, 1, 2, 3, 4, ------ are whole number.


  • Integers (Z) :- All counting numbers, 0 and -ve of counting numbers are called integers.

    Example:- -∞---------, -3, -2, -1, 0, 1, 2, 3, -------∞


  • Rational Numbers (Q) :- A Rational Number is a real number that can be written as a simple fraction

    Example:- {p/q/p,q∈Z}


  • Irrational NUmbers :- An Irrational Number is a real number that cannot be written as a

    simple fraction.

    Example:- √


  • Even numbers :- A number divisible by 2 is called an even number.

    Example:- 0, 2, 4, 6, - - - - - - - - -


  • Odd numbers :- A number not divisible by 2 is called an odd number.

    Example:- 1, 3, 5, 7, - - - - - -


  • Composite Numbers :- Numbers greater than 1 which are not prime, are called composite numbers.

    Example:- 4, 6, 8, 9, 10, - - - -. 6 -> 1,2,3,6.


  • Prime Numbers:- A number greater than 1 having exactly two factors, namely 1 and itself is called

    a prime number.

    Upto 100 prime numbers are:

    2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 71, 73, 79, 83, 89, 97


  • Co-prime Numbers:- Two natural numbers a and b are said to be co-prime if their HCF is 1.

    Example:- (21, 44), (4, 9), (2, 3), - - - - -


  • Twin prime numbers :- A pair of prime numbers (as 3 and 5 or 11 and 13) differing by two are

    called twin prime number.

    Example:- The twin pair primes between 1 and 100 are

    (3, 5), (5, 7), (11, 13), (17, 19), (29, 31), (41, 43), (59, 61), (71, 73).


  • Face value:- Face value is the actual value of the digit.

    Example:- In the number 7635, the "7" has a face value of 7, the face value of 3 is 3 and so on


  • Place value:- The value of where the digit is in the number, such as units, tens, hundreds, etc.

    Example:- In 352, the place value of the 5 is "tens"

    Place value of 2 * 1 = 2;

    Place value of 5 * 10 = 50;

    Place value of 3 * 100 = 300.


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Students can learn and improve on their Cognitive and Mathematical Fast Calculation skills and prepare for competitive examinations like...


  • All I.B.P.S and Public Sector Bank Competitive Exam
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