The Babylonians used a sexagesimal positional number system, analogous to the modern day decimal system. Thus, Babylonian multiplication was very similar to modern decimal multiplication. Because of the relative difficulty of remembering different products, Babylonian mathematicians employed multiplication tables. These tables consisted of a list of the first twenty multiples of a certain "principal number" "n": "n", 2"n", ..., 20"n"; followed by the multiples of 10"n": 30"n" 40"n", and 50"n". Then to compute any sexagesimal product, say 53"n", one only needed to add 50"n" and 3"n" computed from the table.