Knowing that one quantity is numerically equal to another gives us one of the most powerful tools in mathematics, the equation. An equation is simply a statement, usually made with numbers and symbols, that two things are equal.
For example, the simple equation 2 + 3 = 5 states that when the numbers on the left-hand side (i.e. 2 and 3) are combined using the addition operation, the result is equal to the number 5.
This may seem a roundabout way of stating the obvious (mathematics is like that sometimes!), but the principle can be applied to less obvious situations - for example when the values of some of the terms in the equation are not known. We will use a simple equation to understand this better.
For a rectangular figure, Area = Length x Width.
Stated with single letters, the equation can be written A = L x W.
Applying this equation as written, you would be able to calculate A if you know L and W.
It is no surprise that if you know the area and the length, you would be able to calculate the width quite easily. For example if you know the total area of a rectangle is 35 m2, and that the length is 5 metres, what is the width?