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CA Foundation · Quantitative Aptitude · Sequence and Series

The population of a town increases by 20% every year. If the present population is 10,000, what will it be after 2 years?

The population will be 14,400. Growth of 20% a year multiplies the population by 1.2 each year, so after two years it is 10,000 × 1.2² = 14,400. Adding 20% of the original twice gives 14,000, which wrongly ignores compounding.

  1. A14,000
  2. B14,400Correct
  3. C12,400
  4. D12,000

Explanation

Population forms a GP with ratio 1.2: 10,000 × 1.2² = 10,000 × 1.44 = 14,400. The option 14,000 is the linear (simple) growth of 20% of the original each year, which ignores compounding. Check: year 1 = 12,000, year 2 = 14,400.

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