Group Work 3.1.2

U. S. Population Growth

Note: U. S. population 2000: 281.4 million

Table 3.1.2

Year	P (millions)
1960	180.7
1970	205.1
1980	227.7
1990	249.9
1995	261.6

P(t) = 2.30t +181.37

(formula/rule)

Year	t	P (millions)	P(t)	Error
1960	0	180.7	181.37	.67
1970	10	205.1	204.37	.73
1980	20	227.7	227.37	.33
1990	30	249.9	250.37	.47
1995	35	261.6	261.87	.27
			Total Error	2.47

For the population function, P(t), your group constructed on the other side of this paper, answer these questions in complete sentences:

a) What is the verbal interpretation of the slope? Of the intercept?

The population of the U.S. increases 2.30 millions every year.

The population of the U.S. in 1960 was 181.37 million people, according to the model.

b) Predict the U. S. population in the year 2020.

2020 – 1960 = 60 is the value of t needed to find the population in 2020. So, the model predicts 319.37 million people in the U.S. in 2020.

c) In what year will the United States double its present population? (Present population given on opposite side.)

2(281.4 million) = 562.8 million people in the U.S. will occur in 2125. (from my calculator)

d) Suppose the rate of growth doubles, with all other factors remaining constant. What would be the new P(t) function?

P(t) = 4.60t + 181.37