Number System In Maths
Number Systems: Naturals, Integers, Rationals, Irrationals, Reals, and Beyond
The Natural Numbers
The natural (or counting) numbers are 1,2,3,4,5,1,2,3,4,5, etc. There are infinitely many natural numbers. The set of natural numbers, {1,2,3,4,5,…}{1,2,3,4,5,…}, is sometimes written NN for short.
The whole numbers are the natural numbers together with 00.
(Note: a few textbooks disagree and say the natural numbers include 00.)
The sum of any two natural numbers is also a natural number (for example, 4+2000=20044+2000=2004), and the product of any two natural numbers is a natural number (4×2000=80004×2000=8000). This is not true for subtraction and division, though.
Sets
In modern mathematics, just about everything rests on the very important concept of the set .
A set is just a collection of elements, or members. For instance, you could have a set of friends:
F=F= {Abdul, Gretchen, Hubert, Jabari, Xiomara}
or a set of numbers:
Y={−3.4,12,9999}Y={−3.4,12,9999}
There are two methods of representing a set :
(i) Roster or tabular form
(ii) Setbuilder form.
Roster or tabular form: In roster form, all the elements of a set are listed, the elements are being separated by commas and are enclosed within braces { }.
For Example:
Z=the set of all integers={…,−3,−2,−1,0,1,2,3,…}Z=the set of all integers={…,−3,−2,−1,0,1,2,3,…}
Setbuilder form: In the set builder form, all the elements of the set, must possess a single property to become the member of that set.
For Example:
Z={x:x is an integer}Z={x:x is an integer}
You can read Z={x:x is an integer}Z={x:x is an integer} as “The set ZZ equals all the values of xx such that xx is an integer.”
M={x  x>3}M={x  x>3}
(This last notation means “all real numbers xx such that xx is greater than 33 .” So, for example, 3.13.1 is in the set MM , but 22 is not. The vertical bar  means “such that”.)
You can also have a set which has no elements at all. This special set is called the empty set, and we write it with the special symbol ∅∅ .
If xx is a element of a set AA , we write x∈Ax∈A , and if xx is not an element of AA we write x∉Ax∉A .
So, using the sets defined above,
−862∈Z−862∈Z , since −862−862 is an integer, and
2.9∉M2.9∉M , since 2.92.9 is not greater than 33 .
The Integers
The integers are the set of real numbers consisting of the natural numbers, their additive inverses and zero.
{…,−5,−4,−3,−2,−1,0,1,2,3,4,5,…}{…,−5,−4,−3,−2,−1,0,1,2,3,4,5,…}
The set of integers is sometimes written JJ or ZZ for short.
The sum, product, and difference of any two integers is also an integer. But this is not true for division… just try 1÷21÷2.
The Rational Numbers
The rational numbers are those numbers which can be expressed as a ratio between two integers. For example, the fractions 1313 and −11118−11118 are both rational numbers. All the integers are included in the rational numbers, since any integer zz can be written as the ratio z1z1.
All decimals which terminate are rational numbers (since 8.278.27 can be written as 827100827100.) Decimals which have a repeating pattern after some point are also rationals: for example,
0.0833333….=1120.0833333….=112.
The set of rational numbers is closed under all four basic operations, that is, given any two rational numbers, their sum, difference, product, and quotient is also a rational number (as long as we don’t divide by 00).
Rates & Ratios
A ratio is a comparison of two numbers. A ratio can be written using a colon, 3:53:5 , or as a fraction 3535 .
A rate , by contrast, is a comparison of two quantities which can have different units. For example 55 miles per 33 hours is a rate, as is 3434dollars per square foot.
Example 1:
A punch recipe calls for 66 ounces of lime juice, 2121 ounces of apricot juice, and 2121 ounces of pineapple juice. What is the ratio of lime juice to apricot juice?
Writing the ratio using a colon, we get 6:216:21 .
Note that this can be reduced, like a fraction, by dividing both numbers by a common factor — in this case, 33 . In simplest form, the ratio is 2:72:7 .
Example 2:
In the recipe above, what is the ratio of apricot juice to the total amount of punch?
To find the total amount of punch, add 6+21+21=486+21+21=48 .
The ratio of apricot juice to the total amount of punch is 21:4821:48 . But this ratio is probably more clearly written as a fraction, since the apricot juice makes up a fraction of the whole.
21482148
To reduce the fraction, divide both the numerator and the denominator by 33 .
716716
Note that this can be reduced, like a fraction, by dividing both numbers by a common factor — in this case, 33 . In simplest form, the ratio is 2:72:7 .
Example 3:
An adult scolopendromorph centipede has 4646 legs and 88 eyes. In a group of 100100 centipedes of the same species, what is the ratio of legs to eyes?
Note that it doesn’t matter if there are 100100 or 10,00010,000 centipedes; the ratio of legs to eyes will remain the same.
Writing the ratio using a colon, we get 46:846:8 .
Divide both numbers by 22 . In simplest form, the ratio of legs to eyes is 23:423:4 .
Example 4:
A bat beats its wings 170170 times in 1010 seconds. Write the rate as a fraction in lowest terms.
Write the rate as a fraction.
170 wingbeats10 seconds170 wingbeats10 seconds
Divide both the numerator and the denominator by ten.
=17 wingbeats1 second=17 wingbeats1 second
So, the rate is 1717 beats per second.
Example 5:
A mountain climber is 32003200 meters from the peak. He climbs 5050 meters per hour for 88 hours per day. How many days will it be before he reaches the peak?
The first job is to figure out the rate per day.
50 meters1 hour⋅8 hours1 day=50(8)metersday50 meters1 hour⋅8 hours1 day=50(8)metersday
=400metersday=400metersday
He is climbing at a rate of 400400 meters per day.
Now divide 32003200 by the daily rate to find the number of days it will take him to reach the top.
3200 meters400metersday=8 days
Terminating and Repeating Decimals
Any rational number (that is, a fraction in lowest terms) can be written as either a terminating decimal or a repeating decimal . Just divide the numerator by the denominator . If you end up with a remainder of 00 , then you have a terminating decimal. Otherwise, the remainders will begin to repeat after some point, and you have a repeating decimal.
Example 1:
Convert the fraction 5858 to a decimal.
The division is as follows:
0.62585.000 48−− 20 16−− 40 40−− 0 0.62585.000 48_ 20 16_ 40 40_ 0
So, 58=0.62558=0.625 . This is a terminating decimal.
Example 2:
Convert the fraction 712712 to a decimal.
The division is as follows:
0.5833127.0000 6 0−− 1 00 96−− 40 36−− 40 36−− 4 0.5833127.0000 6 0_ 1 00 96_ 40 36_ 40 36_ 4
So:
712=0.583¯712=0.583¯
This is a repeating decimal.
The bar over the number, in this case 33 , indicates the number or block of numbers that repeat unendingly.
The Irrational Numbers
An irrational number is a number that cannot be written as a ratio (or fraction). In decimal form, it never ends or repeats. The ancient Greeks discovered that not all numbers are rational; there are equations that cannot be solved using ratios of integers.
The first such equation to be studied was 2=x22=x2. What number times itself equals 22?
2√2 is about 1.4141.414, because 1.4142=1.9993961.4142=1.999396, which is close to 22. But you’ll never hit exactly by squaring a fraction (or terminating decimal). The square root of 22 is an irrational number, meaning its decimal equivalent goes on forever, with no repeating pattern:
2√=1.41421356237309…2=1.41421356237309…
Other famous irrational numbers are the golden ratio, a number with great importance to biology:
1+5√2=1.61803398874989…1+52=1.61803398874989…
ππ (pi), the ratio of the circumference of a circle to its diameter:
π=3.14159265358979…π=3.14159265358979…
and ee, the most important number in calculus:
e=2.71828182845904…e=2.71828182845904…
Irrational numbers can be further subdivided into algebraic numbers, which are the solutions of some polynomial equation (like 2√2 and the golden ratio), and transcendental numbers, which are not the solutions of any polynomial equation. ππ and ee are both transcendental.
The Real Numbers
The real numbers is the set of numbers containing all of the rational numbers and all of the irrational numbers. The real numbers are “all the numbers” on the number line. There are infinitely many real numbers just as there are infinitely many numbers in each of the other sets of numbers. But, it can be proved that the infinity of the real numbers is a bigger infinity.
The “smaller”, or countable infinity of the integers and rationals is sometimes called ℵ0ℵ0(alefnaught), and the uncountable infinity of the reals is called ℵ1ℵ1(alefone).
There are even “bigger” infinities, but you should take a set theory class for that!
The Complex Numbers
The complex numbers are the set {a+bia+bi  aa and bb are real numbers}, where ii is the imaginary unit, −1−−−√−1.
The complex numbers include the set of real numbers. The real numbers, in the complex system, are written in the form a+0i=aa+0i=a. a real number.
This set is sometimes written as CC for short. The set of complex numbers is important because for any polynomial p(x)p(x) with real number coefficients, all the solutions of p(x)=0p(x)=0 will be in CC.
Monomials, Binomials, Polynomials
A monomial is any product of numbers and variables, like 1717 , or 3xy3xy , or −4x2−4×2 , or
7100a5b6c7d8z9997100a5b6c7d8z999
The only rules are that the variables should be raised to only positive integer powers (no square roots or 1x1x ‘s allowed), and no plus or minus signs.
The coefficient of a monomial is the numerical part. For example, in the above examples, the coefficients are 17,3,−417,3,−4 and 710710 .
A binomial is the sum of two monomials, for example x+3x+3 or 55x2−33y255×2−33y2 or
7100a5b6c7d8z999−13x7100a5b6c7d8z999−13x
A trinomial is the sum of three monomials.
A polynomial is the sum of nn monomials, for some whole number nn . So monomials, binomials and trinomials are all special cases of polynomials. A polynomial can have as many terms as you want.
The degree of a monomial is the sum of the exponents of all its variables. The degree of a polynomial is the term of the polynomial that has the highest degree.
Beyond…
There are even “bigger” sets of numbers used by mathematicians. The quaternions, discovered by William H. Hamilton in 18451845, form a number system with three different imaginary units!
Number System Question



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



 Whole numbers (W) : All counting numbers together with zero from the set of whole numbers
Example: 0, 1, 2, 3, 4, —— are whole number.
 Whole numbers (W) : All counting numbers together with zero from the set of whole numbers



 Integers (Z) : All counting numbers, 0 and ve of counting numbers are called integers.
Example: ∞———, 3, 2, 1, 0, 1, 2, 3, ——∞
 Integers (Z) : All counting numbers, 0 and ve of counting numbers are called integers.



 Rational Numbers (Q) : A Rational Number is a real number that can be written as a simple fraction
Example: {p/q/p,q∈Z}
 Rational Numbers (Q) : A Rational Number is a real number that can be written as a simple fraction



 Irrational NUmbers : An Irrational Number is a real number that cannot be written as a
simple fraction.
Example: √
 Irrational NUmbers : An Irrational Number is a real number that cannot be written as a



 Even numbers : A number divisible by 2 is called an even number.
Example: 0, 2, 4, 6, – – – – – – – – –
 Even numbers : A number divisible by 2 is called an even number.



 Odd numbers : A number not divisible by 2 is called an odd number.
Example: 1, 3, 5, 7, – – – – – –
 Odd numbers : A number not divisible by 2 is called an odd number.



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



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



 Coprime Numbers: Two natural numbers a and b are said to be coprime if their HCF is 1.
Example: (21, 44), (4, 9), (2, 3), – – – – –
 Coprime Numbers: Two natural numbers a and b are said to be coprime if their HCF is 1.



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



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


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

 1. What is the place value of 7 in the numeral 2734?
Answer: Option ‘C’
7 × 100 = 700
 2. What is the place value of 3 in the numeral 3259
Answer: Option ‘D’
3 × 1000 = 3000
 3. What is the diffference between the place value of 2 in the numeral 7229?
Answer: Option ‘C’
200 – 20 = 180
 4. What is the place value of 0 in the numeral 2074?
Answer: Option ‘D’
Note : The place value of zero (0) is always 0. It may hold any place in a number,
its value is always 0.