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Text 1
Populations tend to grow at an exponential rate. This means that they progressivel, double. As an example of this type of growth rate, take one penny and double it every day for one month. After the first week, you would have only 64 cents, but after the fourth week you would have over a million dollars.
This helps explain why the population has come on "all of a sudden". It took from the beginning of human life to the year 1830 for the population of the earth to reach one billion. That represents a time span of at least two million years. Then it took from 1830 to 1930 for world population to reach 2 billion. The next billion was added by 1960, only thirty years, and in 1975 world population reached 4 billion, which is another billion people in only Fifteen years.
World population is increasing at a rate of 9,000 per hour, 220,000 per day, 80 million per year. This is not only due to higher birth rates, but to lower death rates as
A. 100 years
B. 145 years
C. 1975 years
D. Over two million years