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Demographic math

Learn to calculate a population’s doubling time and predict future size using growth rate formulas. Practice with examples and apply the Pert equation. Quiz included for checking understanding.

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Demographic math

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  1. 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

  2. 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?

  3. 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?

  4. Calculating future population size • A = Pert • A = future population size • P = current population size • Constant e = 2.72 • Growth rate r reported as percent of percent • T = time

  5. A = Pert • Try one! • The US population this year is 306 million and our growth rate is .6%. How large will the population be in 2050?

  6. Try another one!  • The world’s population is about 677 million and our growth rate is 1.2%. Assuming the rate stays constant, how big will the population be by 2050? By 2100?

  7. Check for understanding • What two calculations did you just learn how to do? • What can you use A = Pert for? • Which equation is simpler? • What is the common mistake that is made in the A = Pert formula?

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