In many applications of mathematics, we can express numbers as power of some given base. We can reverse this question and ask, for example, “what exponent of 3 gives 27? Our attention is then turned to the index itself. This leads to the notion of a logarithm, which is simply index. Logarithms appear in all sorts of calculations in engineering and science, business and economics. In this unit, we will learn about indices and logarithms and rules for manipulating them through a number of worked examples.