Page 2 - LN

 We can use any letter as a variable, but only lowercase English alphabets.

 Numbers cannot be used for the variable as they have a fixed value.
.

Example:
Karan wanted to buy story books from a bookstall. She wanted to buy 3 books for
herself, 2 for her brother and 4 for 2 of her friends. Each book cost Rs.15.how much
money she should pay to the shopkeeper?
Solution:

Cost of 1 book = Rs.15
We need to find the cost of 9 books.

No. of
notebooks 1 2 3 4 ……. a ….....

Total cost 15 30 45 60 ……. 15 a …….

In the current situation, a (it’s a variable) stands for 9
Therefore,

Cost of 9 books = 15 × 9
= 135

Therefore Karan needs to pay Rs.135 to the shopkeeper of the bookstall.
The variable and constant not only multiply with each other but also can be added or
subtracted, based on the situation.

Constant:
These are the numbers which will be having fixed value.
Use of Variables in Common Rules (Geometry)
1. Perimeter of Square
The perimeter of a square = Sum of all sides

= 4 × side
= 4s

Thus, p = 4s

Here s is variable, so the perimeter changes as the value of side change.
2. Perimeter of Rectangle
Perimeter of rectangle = 2(length + breadth)

= 2 (l + b) or 2l + 2b
Thus, p + 2 × (l + b) or 2l + 2b