Chapter 1 - 1.1 - Graphs of Equations - 1.1 Exercises - Page 80: 77b

Graphically: $74.7$ years Algebraically: $74.7$ years

$$t=1990-1940=50$$ Graphically as shown in the graph, the life expectancy is about $74.7$ years. Algebraically, $$y=\frac{63.6+0.97(50)}{1+0.01(50)}=74.7$$ Thus, algebraically, the life expectancy is about $74.7$ years.