To attract more visitors, zoo authority announces 20% discount on every ticket which cost 25 paise. For this reason, sale of ticket increase by 28%. Find the percentage of increase in the number of visitors ?

Let the number of visitors in the beginning = 100
$$\eqalign{ & {\text{Total revenue}} \cr & = 0.25 \times 100 \cr & = {\text{Rs}}{\text{. 25}} \cr & {\text{New price}} \cr & = 25 \times \frac{{80}}{{100}} \cr & = 0.20{\text{ or 20 paise}} \cr & {\text{New revenue}} \cr & = 25 \times \frac{{128}}{{100}} \cr & = {\text{Rs}}{\text{. 32}} \cr & {\text{Number of visitors now}} \cr & = \frac{{32}}{{0.20}} \cr & = 160 \cr & {\text{Change in number of visitor }}\% \cr & = \frac{{160 - 100}}{{100}} \times 100 \cr & = 60\% \cr} $$