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.

The number before an alphabet (variable) is called a constant.

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.

Identify the constants and the variables in each of the following :-

i) 8a

Constant = 8 ; Variable = a

ii) 3d

Constant = 3 ; Variable = d

iii) 4t

Constant = 4 ; Variable = t

iv) ab

Constant = 0 ; Variable = ab

v) 44

Constant = 44 ; Variable = none

vi) 21ac

Constant = 21 ; Variable = a and c

vii) 13r

Constant = 13 ; Variable = r

viii) 23s

Constant = 23 ; Variable = s

ix) 3 rd

Constant = 3 ; Variable = r and d

x) 24 th

Constant = 24 ; Variable = t and h

• Addition of Literals

• Subtraction of Literals

• Multiplication of Literals

• Division of Literals

• Constants and Variables

• Coefficient

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