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Demographic math Two things you will be able to do at the end of this lesson: Calculate a population’s doubling time Predict future population size Please get out a calculator
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Doubling time Formula: Time =70 r r= growth rate Example: a country is growing at 2% a year. In how many years will the county’s population double?
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Practice The Ivory Coast is growing at 3.8% each year. In how many years will it double? China is growing at 1.2%. In what year will China’s population be double what it is today?
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Calculating future population size A = Pe rt A = future population size P = current population size Constant e = 2.72 Growth rate r reported as percent of percent T = time
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A = Pe rt Try one! The US population this year is 306 million and our growth rate is.6%. How large will the population be in 2050?
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Try another one! The world’s population is about 7.058 billion and our growth rate is 1.2%. Assuming the rate stays constant, how big will the population be by 2050? By 2100?
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Check for understanding What two calculations did you just learn how to do? What can you use A = Pe rt for? Which equation is simpler? What is the common mistake that is made in the A = Pe rt formula?
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Check your answers! 1. 405.5 million 2. 1.28 billion 3. 8.5 billion 4. More developed: 700 years Less developed: 41 years
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Back side! China – 1999 – 70 years; 1.83 billion 2000 – 77.7 years; 1.88 billion 2014 – 140 years; 1.6 billion
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India 1999 – 36.8 years; 2.59 billion 2000 - 38.8 years; 2.45 billion 2014 – 46.6 years; 2.21 billion
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