A town has population of 20,000 in 1980. In one year i.e by 1981 it increased by 25%. Next year i.e in 1982, it decreased by 20%. The next year in 1983 there was an increase of 30%. What is the population at end of 1983?

26000

(1981, Inc. by 25%) ⇒ 125% = \(\frac{5}{4}\)

(1982, Dec. by 20%) ⇒ 80% = \(\frac{4}{5}\)

(1983, Inc. by 30%) ⇒ 130% = \(\frac{13}{10}\)

AQT

Population in 1980 = 20000

Population by 1981 = 20000 × 125% = 20000 × \(\frac{5}{4}\) = 25000

Population by 1982 = 25000 × 80% = 20000 × \(\frac{4}{5}\) = 20000

Population by 1983 = 20000 × 130% = 20000 × \(\frac{13}{10}\) = 26000

Hence,

Population at the end of 1983 = 26,000