# Constants and Variables

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Constants and Variables : Constants are fixed number and variables are literals.

The diameter, d of a circle of radius r is given by the formula d = 2r. In this formula, 2 is a fixed number whereas the literal numbers d and r are not fixed because they depend upon the size of the circle. For circles of different sizes, the values of d and r will be different.

It follows from the above examples that in Algebra, we come across two types of symbols namely constants and variables as defined below.

Constant : A symbol having a fixed numerical value is called a constant.
OR
The number before an alphabet (variable) is called a constant.

Variable : A symbol which takes various numerical values is called a variable.
OR
The alphabet after a number (constant) is called a variable.

In the formulas d = 2r; 2 is a constant whereas, r and d are variables.

Note: In some situations, literal numbers are also treated as constants. In such situations, it is presumed that the particular literal number will take a few fixed values.

Examples :

Identify the constants and the variables in each of the following :-
i) 8a
Solution :
Constant = 8 ; Variable = a

ii) 3d
Solution :
Constant = 3 ; Variable = d

iii) 4t
Solution :
Constant = 4 ; Variable = t

iv) ab
Solution :
Constant = 0 ; Variable = ab

v) 44
Solution :
Constant = 44 ; Variable = none

vi) 21ac
Solution :
Constant = 21 ; Variable = a and c

vii) 13r
Solution :
Constant = 13 ; Variable = r

viii) 23s
Solution :
Constant = 23 ; Variable = s

ix) 3 rd
Solution :
Constant = 3 ; Variable = r and d

x) 24 th
Solution :
Constant = 24 ; Variable = t and h

Introduction to Algebra