What is the common difference between the elements of the arithmetic sequence below?
–18, –22.5, –27, –31.5, –36

In mathematics, an arithmetic progression (AP) or arithmetic sequence is a sequence of numbers such that the difference between the consecutive terms is constant. The common difference would be calculated as follows:


–36 - –31.5  = - 4.5 
–27 - –22.5  = -4.5

Therefore, the common difference is -4.5.