Answer:
1975------ 4.8%
1990 ------ 11.48%
1985 ------ 8.51%
Step-by-step explanation:
Given
[tex]P(t) = 0.04t + 4.6[/tex] if 0 ≤ t < 10
[tex]P(t) = -0.01005t^2 + 0.945t - 3.4[/tex] if 10 ≤ t ≤ 30
Where
t:=0 implies year = 1970
Solving (a): Beginning of 1975.
First, we calculate the value of t
[tex]t = 1975 - 1970[/tex]
[tex]t = 5[/tex]
This falls in the range: 0 ≤ t < 10
So:
[tex]P(t) = 0.04t + 4.6[/tex]
[tex]P(5) = 0.04 * 5 + 4.6[/tex]
[tex]P(5) = 4.80[/tex]
Solving (b): Beginning of 1990.
[tex]t = 1990 - 1970[/tex]
[tex]t = 20[/tex]
This falls in the range: 10 ≤ t ≤ 30
So:
[tex]P(t) = -0.01005t^2 + 0.945t - 3.4[/tex]
[tex]P(20) = -0.01005*20^2 + 0.945*20 - 3.4[/tex]
[tex]P(20) = 11.48[/tex]
Solving (c): Beginning of 1985
[tex]t = 1985 - 1970[/tex]
[tex]t = 15[/tex]
This falls in the range: 10 ≤ t ≤ 30
So:
[tex]P(t) = -0.01005t^2 + 0.945t - 3.4[/tex]
[tex]P(15) = -0.01005*15^2 + 0.945*15 - 3.4[/tex]
[tex]P(15) = 8.51375[/tex]
[tex]P(15) = 8.51[/tex]