A town's population rose by 20% in the first year, fell by 20% in the second year and rose by 10% in the third year. It is now 52,800. What was the population three years ago?

Explanation

1. 01

   Overall factor = $1.2 \times 0.8 \times 1.1$.

2. 02

   $1.2 \times 0.8 = 0.96$, and $0.96 \times 1.1 = 1.056$.

3. 03

   Original = $\frac{52800}{1.056} = 50{,}000$.