Numerical answer
The population of a town increases by 20% in the first year, decreases by 10% in the second year, and increases by 25% in the third year. If the population at the end of the third year is 8100, find the population at the start of the first year.
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Answer: 6000
Net multiplying factor over three years = 1.20 × 0.90 × 1.25 = 1.35. If P is the initial population, P × 1.35 = 8100, so P = 8100/1.35 = 6000. Verify: 6000 → 7200 (year 1) → 6480 (year 2) → 8100 (year 3). Matches.
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