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Question
The population of a town was decreasing every year due to migration, poverty and unemployment. The present population of the town is 6,31,680. Last year the migration was 4% and the year before last, it was 6%. What was the population two years ago?
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Solution
Let the population two years ago = P (Principal)
Present population of the town = A = 631680
Rate of migration in 1st year = 4%
Rate of migration in 2nd year = 6%
By using the formula,
`A = P(1 - R/100)(1 - R/100)`
⇒ `631680 = P(1 - 4/100)(1 - 6/100)`
⇒ `631680 = P xx 24/25 xx 47/50`
⇒ `P = (631680 xx 25 xx 50)/(24 xx 47)`
⇒ P = 560 × 1250 = 700000
Hence, the population of town was 700000 two years ago.
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