Question 21

The population of a city has been increasing at 5% every year. The present population is 185220. What was its population 3 years back?

Solution

let the population 3 years back be x

according to the question

$$ x \times \frac{105}{100} \times \frac{105}{100} \times \frac{105}{100} = 185220 $$

$$ x = \frac{185220 \times 20 \times 20 \times 20}{21 \times 21 \times 21} $$

solving x = 160000

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