The population of a city increases at the rate of 5% pa. If the present population of the city is 185220, then what was its population 3 yr ago?

Given, P = 185220 R = 5% (increases) and n = 3 yr
According to the formula,
Population n yr ago = P/(1 + R/100)ⁿ
= 185220/(1 + 5/100)³
= 185220/[(21/20) x (21/20) x (21/20)]
= [185220 x 20 x 20 x 20] / [21 x 21 x 21]
= 20 x 20 x 20 x 20
= 160000