Percentage > IMPORTANT FACTS AND FORMULAE
Concepts of Percentage : By a certain percent, we mean that many hundredths. Thus, x percent means x hundredths, written as x%. To express x% as a fraction : we have, x% = x/100. To express a/b as a percent : we have, a/b = (a/b×100)% . 

Results on population : Let the population of a town be P now and suppose it increases at the rate of R% per annum, then : Population after n years = P[1+R/100]^{n}. Population n years = p / [1+R/100]^{n}. 