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Question
The annual rate of growth in population of a town is 10%. If its present population is 26620, then the population 3 years ago was _________
Solution
₹ 20,000
Explanation;
Hint:
Rate of growth of population r = 10%
Present population = 26620
Let population 3 years ago be x
∴ Applying the formula for population growth which is similar to compound interest,
26620 = `x(1 + "r"/100)^3`
∴ 26620 = `x(1 + 10/100)^3`
= `x(110/100)^3`
∴ x = `26620 xx (100/110)^3`
= ₹ 20,000
The population 3 years ago was ₹ 20,000
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