Tips and Tricks- Successive Discounts

Formula for successive discounts
a+b+(ab/100)
This is used for successive discounts types of sums.like 1999 population increases by 10% and then in 2000 by 5% so the population in 2000 now is 10+5+(50/100)=+15.5% more that was in 1999 and if there is a decrease then it will be preceded by a -ve sign and likewise.