Classification of
Numbers:
To classify the various
kinds of numbers that we deal in
algebra. The counting numbers or natural numbers are the numbers,
i.e N={1,2,3,4,…}. The three dots, called an
ellipsis, indicates the pattern continues indefinitely. As their name implies,
these numbers
Often
used to count things. For example, there are 26 alphabet; there are 100 cents
in a dollar. The whole numbers are the numbers
i.e
W={0,1,2,3,4,5,…}. The whole numbers are
also counting numbers with 0. The integers are the numbers
i.e
Z={ …,-3,-2,- 1,0,1,2,3,… }. These numbers are very useful. These numbers are
used in many situations. E.g if your checking
account
has $10 in it and you write a check for $15, you can represent the current balance as -$5.
It must notice that the
counting numbers are included among the whole numbers . Every time we expand a
number system. Such as
From the whole numbers
to the integers, we do so in order to be able to handle new, and usually more
complicated problems. Thus
The
integers allow us to solve problems requiring both positive and negative
counting numbers, such as profit /loss, height
above/below
sea level, temperature above/below 0°F, and so on. But
integers alone are not sufficient for all
problems.
What part of a dollar is 38 cents? Or what part of pound is 5 ounces? We are
unable to give answer by using integers
.
To
answer these type of questions we enlarge number system to include rational
numbers. For example 38/100 answers the
question
“ what part of a dollar is 38
cents?” and 5/16 answers the question
“what part of a pound is 5 ounces?.”
RATIONAL
NUMBER:
Rational
number is a number that can b expressed as a quotient a/b of two integers, The
integer “a” is called the
numerator,
and the integer “b” is called “ denominator” it can not be zero ( 0 ).
Examples
of rational numbers are following. 3/4, 5/2, 0/6, - 2/3 etc. since a/1 = a for any integer a., it
allows rational numbers contain the integers
Special
case .

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