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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