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Natural Numbers

Natural numbers are counting numbers, i.e., the numbers which we use to count. For example, 1, 2, 3,…The lowest natural number is 1.

Whole Numbers

When zero is included in the list of natural numbers, the numbers are known as whole numbers. For example, 0, 1, 2,…The lowest whole number is 0.


Integers are whole numbers, the negative of whole numbers and zero.
For example, 43,434235, 28, 2, 0, −28, and −3030 are integers, but numbers like 1/2, 4.00032, 2.5, Pi, and −9.90 are not whole numbers.

Number Line

The number line is used to represent the set of real numbers. A representation of the number line is given below:

Description: 1-1.tif

Properties of Number Line

  • The number line goes on till infinity in both directions. This is indicated by the arrows.
  • Integers greater than zero are called positive integers. These numbers are to the right of zero on the number line.
  • Integers less than zero are called negative integers. These numbers are to the left of zero on the number line.
  • •The integer zero is neutral. It is neither positive nor negative.
  • •The sign of an integer is either positive (+) or negative (), except zero, which has no sign.
  • •Two integers are the opposites if each of the two are at the same distance from zero, but on the opposite side of the number line. One will have a positive sign while the other a negative sign. In the number line above, +3 and −3 are labelled as opposites. In other words, the whole negative number scale looks like a mirror image of the positive number scale, with a number like 15 being at the same distance away from 0 as the number 15 is.
  • •The number half-way between 1 and 2 is 1.5; just as the number halfway between 1 and 2 is 1.5.
  • •We represent positive numbers without using a +ve sign.
    For example, we would write 29.1 instead of +29.1. But when we talk of negative numbers, the sign must be there.

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