Q. A. – Elementary Concepts of Number System

In Maths it is necessary that your fundamentals are strong.  Therefore, to recap for those who are not very strong in Quantitative       Aptitude, we provide some elementary concepts of number system:–

1.          Natural Numbers:  Counting numbers 1, 2, 3, 4,…………. Are known as natural numbers. Natural numbers are denoted by any numbers in the     set {1, 2, 3, 4,……}

1.          Whole Numbers: All the  natural numbers and 0 constitute  whole numbers. They are denoted by any number in the set {0, 1, 2, 3,   4,…………}
2.           Even Numbers: A numbers exactly divisible by 2 is called an even number, example- 2, 4, 6, 8,…..
3.          Odd Numbers:  A numbers not divisible by 2 is called an odd number,  example- 1, 3, 5, 7,………
4.            Prime Numbers:              A numbers which has no factor except itself and unity is a prime number, example- 2, 3, 5, 7, 11, 13,………

1.             Least Common Multiplier (LCM): For two or more numbers the smallest positive numbers in the set of common multiples is  the LCM. For     example, the LCM for 4 and 5 is = 20.
2.          Least Common Denominator (LCD):        For two or more fractions, the LCD is the LCM of their denominators.

For example, for 1/3, ½ and ¼, the LCD is 12.

1.         Reciprocal or Multiplicative Inverse: A number that, when used to multiply a given number, gives a product of 1 is a reciprocal or   multiplicative inverse.

                 For example -   (4 / 5) x  (5 / 4) = 1;     5 / 4  is the reciprocal of  4 / 5

1.          Additive Inverse:   A number that, when added to a given number, gives a sum of zero is an additive inverse. For example, 4 + (-4) is the  additive inverse of 4.

1.              Place Value and Face Value :      Value of a digit in a numeral is defined as the  value of the place that  digit has in the numeral.

                For example, in the numeral 43,269

              The place value of 9 is units = 9

              The place value of 6 is 6 tens = 60

              The place value of 2 is 2 hundreds = 200

              The place of value of 3 is 3 thousands = 3,000 and so on.

 The face value of a digit in a numeral is the value of the digit itself at whatever place it may be. For example- in the numeral,    23,265, the face     value of 5 here is 5 and of 6 is 6.

1.                 Integer:                   An integer is any number in the set {…..-3, -2, -1, 0, 1, 2, 3,……}

1.              Rational Number :           Any number in the set {all numbers that can be written in the from p/q, where p and q are integers and q is not zero) is a rational number. For example, 1/3 = 0.33333…., and ¼ = 0.25

1.         Irrational Number: Any number in the set {all numbers that do not have repeating or terminal decimal representations} is an irrational number.

    For example – 2 , 1, 

    Real Number:    Any number in the set {all rational and irrational numbers} is a real number.

            Absolute value:   The absolute value of a number is the equivalent positive value.  For example- |+2| = +2and |-3| = +3.

1.                Real Number:    Any number in the set {all rational and irrational numbers} is real number.
2.                 Absolute value:  The absolute value of a number is the equivalent positive value. For example- |+2| = +2and |-3| = +3.