If in 1997 , 1998 and 1999 a worker received 10% more in salary each year than he did the previous year, how much did he receive in 1999 than in 1997 ?

Say, salary in 1997 was Tk. 10 In each year, he received 10% more than the previous year In 1997, salary = 10 In 1998, salary = 10 + 1 = Tk. 11 In 1999, salary = 11 + 11x (10/100) = 11 + 1.1 = 12.1 % Difference = (Changex100)/Origina = (12.1 - 10)x100/10 = 21%