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In one year, the population, of a village increased by 10% and in the next year, it decreased by 10%. If at the end of 2nd year, the population was 7920, what was it in the beginning?

Correct answer: B. 8000

  • A. 8500
  • B. 8000
  • C. 8100
  • D. 8400Downloading Interactive Party Trivia Games

Explanation

Let the initial population be P. After a 10% increase and then a 10% decrease, it becomes P x 1.10 x 0.90 = 0.99P, so 0.99P = 7920 and P = 7920/0.99 = 8000. Students may choose 8500 by treating the two 10% changes as a net increase or decrease of 20%.

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