What is an Equation? Equations and Formulas
An equation says that two things are equal. It will have an equals sign “=” like this:
x  +  2  =  6 
That equations says: what is on the left (x + 2) is equal to what is on the right (6)
So an equation is like a statement “this equals that“
What is a Formula?
A formula is a fact or rule that uses mathematical symbols.
It will usually have:
 an equals sign (=)
 two or more variables (x, y, etc) that stand in for values we don’t know yet
It shows us how things are related to each other.
Example: The formula for finding the volume of a box is:
V = lwh
V stands for volume, l for length, w for width, and h for height.
When l=10, w=4, and h=5, then:
V = 10 × 4 × 5 = 200
These are all equations, but only some are formulas:
x = 2y – 7  Formula (relating x and y) 
a^{2} + b^{2} = c^{2}  Formula (relating a, b and c) 
x/2 + 7 = 0  Not a Formula (just an equation) 
Subject of a FormulaThe “subject” of a formula is the single variable (usually on the left of the “=”) that everything else is equal to. Example: in the formulas = ut + ½ at^{2} “s” is the subject of the formula
Changing the SubjectA very powerful thing that Algebra can do is to “rearrange” a formula so that another variable is the subject. Example: Rearrange the volume of a box formula (V = lwh) so that the width is the subjectStart with:V = lwh divide both sides by h:V/h = lw divide both sides by l:V/(hl) = w swap sides:w = V/(hl) So if we want a box with a volume of 12, a length of 2, and a height of 2, we can calculate its width: w =V/(hl) =12 / (2 × 2) =12 / 4 =3
