Why numbers with a decimal point aren't the only decimal numbers

Question

This is for an essay I have to do for math. Please respond quickly.

Answer 1

The Decimal Number System is a positional number system.  This means that each digit has a value that is multiplied by a power of 10.  For example,

     123.4  means  1*10² + 2*10¹ + 3*10⁰ + 4*10^-1

 

When all values to the right of the decimal point are zero, the value is a whole number (an integer) and we may omit the decimal point and the following zeros.  So, we may write either

     12 or 12.00      [note:  actually, these have different precision]

 

This means that all of the positive integers (1, 2, 3, 4, 5, 6, 7, 8, ...) are decimal numbers without a decimal point although they are still decimal numbers.

 

There are other number systems.  Here is a number in the Binary Number System (also a positional number system):

   1011.001₂

And, here is a number in the Octal Number System:

   125.33₈

And, here is a number in the Hexadecimal Number System:

  A.BAD₁₆

 

 

In answer to Mark M's comment:

 

The fraction  1/4 is a rational number.    [note:  1 and 4 are decimal here]

Expressed as a Decimal Number, decimal  1/4 is 0.25₁₀               [this is 25/100]
Expressed as a Binary Number, decimal 1/4 is 0.01₂                   [this is 1/4]
Expressed as an Octal Number, decimal 1/4 is 0.2₈                     [this is 2/8]
Expressed as a Hexadecimal Number, decimal 1/4 is 0.4₁₆           [this is 4/16]

Some Decimal Numbers have repeating fractional values.  For example, 0.3333333…

Some Decimal Number fractions do not repeat. 
     For example, Pi= 3.14159265…