The population of a town decreased by 12% during 1998 and then increased by 8% during 1999. Find the population of the town, at the beginning of 1998, if at the end of 1999 its population was 285120.

Let population in the beginning of 1998 be x.

Given,

The population of a town decreased by 12% during 1998 and then increased by 8% during 1999.

Population at the end of 1999 = 285120.

$\therefore 285120 = x\Big(1 - \dfrac{12}{100}\Big)\Big(1 + \dfrac{8}{100}\Big) \\[1em] \Rightarrow 285120 = x \times \dfrac{88}{100} \times \dfrac{108}{100} \\[1em] \Rightarrow 285120 = \dfrac{9504x}{10000} \\[1em] \Rightarrow x = \dfrac{285120 \times 10000}{9504} \\[1em] \Rightarrow x = 300000.$

Hence, population of town at beginning of 1998 = 300000.