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Chapter 8: Problem 12

Define the crude birthrate (CBR) and the crude death rate (CDR). Describe how these rates are used to calculate the percent rate of growth and the doubling time of a population.

Short Answer

Expert verified
The crude birthrate (CBR) is the number of live births per 1,000 people in a population in a given year, while the crude death rate (CDR) is the number of deaths per 1,000 people in a population in a given year. The percent rate of growth is calculated by subtracting the CDR from the CBR and dividing by 10. The doubling time, or the time it takes for a population to double, is calculated by dividing 70 by the percent rate of growth.

Step by step solution

01

Define the Crude Birthrate (CBR)

The Crude Birthrate (CBR) is the number of live births per 1,000 people in a population in a given year.
02

Define the Crude Death Rate (CDR)

The Crude Death Rate (CDR) is the number of deaths per 1,000 people in a population in a given year.
03

Calculate the percent rate of growth

The percent rate of growth of a population can be calculated by subtracting the CDR from the CBR, dividing the result by 10. This equation can be represented as follows: \[ro = \frac{(CBR - CDR)}{10}\], where ro is the annual growth rate in percent.
04

Determine the doubling time

To determine the doubling time of a population, the rule of 70 is commonly used. This rule states that to find the number of years it takes for a population to double, divide 70 by the annual growth rate. Mathematically, it is represented as \[Dt = \frac{70}{ro}\], where Dt is the doubling time, and ro is the annual growth rate in percent as calculated in step 3.

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