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According to a Census Taken Towards the End of the Year 2009, the Population of a Rural Town Was Found to Be 64,000. the Census Authority Also Found that the Population of this Particular Town Had

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Question

According to a census taken towards the end of the year 2009, the population of a rural town was found to be 64,000. The census authority also found that the population of this particular town had a growth of 5% per annum. In how many years after 2009 did the population of this town reach 74,088 ?

Sum
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Solution

Population in 2009 (P) = 64,000
Let after n years its population be 74,088(A)
Growth rate= 5% per annum

∴ A = `"P"( 1 + r/100 )^n`

⇒ `(74,088)/(64,000) = (21/20)^n`

⇒ `( 9,261)/(8,000) = ( 21/20)^n`

⇒ `(21/20)^3 = ( 21/20)^n`

On comparing, we get,
n = 3 years

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Concept of Compound Interest - When the Time is Not an Exact Number of Years and the Interest is Compounded Yearly
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Chapter 3: Compound Interest (Stage 2) [Applications] - Exercise 3 (D) [Page 53]

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Selina Concise Mathematics [English] Class 9 ICSE
Chapter 3 Compound Interest (Stage 2) [Applications]
Exercise 3 (D) | Q 3 | Page 53

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