In 1993, the life expectancy of males in a certain country was 68.3 years. In 1999, it was 70.8 years. Let E represent the life expectancy in year t and let t represent the number of years since 1993.

The linear function E(t) that fits the data is E(t) = 0.4t+68.3 (Round to the nearest tenth.)

Use the function to predict the life expectancy of males in 2007. E(14) = _74.1______. (Round to the nearest tenth.)

Solution:

We assume E(t)= 68.3+At

so when t= 0, in 1993, E=68.3

t=6, in 1999, E=68.3+6A= 70.8

A= 0.417, if nearest tenth, that is 0.4

E(t) = 0.4t+68.3

E(14)= 68.3+0.417*14= 74.13