In a certain sense, decreases are reciprocals of increases. You can calculate the reciprocal of each “faster”, or you can work with the figures as given and wha

In a certain sense, decreases are reciprocals of increases. You can calculate the reciprocal of each “faster”, or you can work with the figures as given and what you want is the reciprocal of the final result. This follows from the elementary fact that division is the same as multiplication by the reciprocal and we are only treating multiplication and division.