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The population of a country has increased at a rate of 2.7% every year for 5 years. If...

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sophiaba | Student, Grade 10 | eNoter

Posted October 10, 2011 at 2:22 AM via web

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The population of a country has increased at a rate of 2.7% every year for 5 years. If the present population is 15.2 million, what was it five years ago?

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justaguide | College Teacher | (Level 2) Distinguished Educator

Posted October 10, 2011 at 2:53 AM (Answer #1)

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The present population of the country is 15.2 million = 15.2*10^6. The population has grown at 2.7% per year for 5 years.

Let the population five years ago be P.

P*(1.027)^5 = 15.2*10^6

=> P = 15.2*10^6/(1.027)^5

=> P = 13.3*10^6

The population 5 years ago was 13.3 million

 

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sophiaba | Student, Grade 10 | eNoter

Posted October 10, 2011 at 3:29 AM (Answer #2)

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@justaguide thanks but I'm supposed to be using series and sequences notation, like U1, U5.. And I'm supposed to be solving with the geometric sequence formulas such as    Un = U1 * r^n

r is the ratio by which you multiply a term to get the one after it in a geometric sequence

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