A formula is a relation between certain quantities. A relations (equation) between two or more quantities is called a formula. For example, if ‘l’ is the length of a rectangle and ‘b’ = the breadth of the rectangle, its perimeter ‘p’ can be expressed by the following formula that you are already familiar with.  P = 2 ( l + b )

Literals are used to represent the variables or quantities in a formula, certain literals are traditionally used to represent particular quantities

If you know the values of all expect one of the quantities in a formula, you can work out the unknown quantity. let us consider a few formulae you have come across earlier.

Examples -

 1) The perimeter ‘p’ of a square is four times of its side ‘a’. this can be represented by the formula p = 4a

 2) The volume ‘Vv’ of a cuboid is the product of its length ‘Ll’, breadth ‘Bb’ , and height ‘Hh’. This is expressed by the formula, Vv = Ll X Bb X Hh

 3) The work done ‘Ww’ is the product of the force ‘Ff’ and the distance ‘Dd’ through which a body moves. then the formula is  Ww = Ff X Dd

 4) Suppose the sum of two numbers is 20, then the required formula is y + z = 20, y &  are the unknown numbers.