# Statistics on life expectancies

I don't understand how to solve the last the questions of this problem. Can anybody help me with this.

[The table shows the life expectancies of a child (at birth) in the United States for selected years from 1940 through 2010. (Source: U.S. National Center for Health Statistics)

• 1940 - 62.9

• 1950 - 68.2

• 1960 - 69.7

• 1970 - 70.8

• 1980 - 73.7

• 1990 - 75.4

• 2000 - 76.8

• 2010 - 78.7

A model for the life expectancy during this period is y = (63.6 + 0.97t)/ (1 + 0.01t) , 0≤t≤70

where y represents the life expectancy and t is the time in years, with t = 0 corresponding to 1940. (a) Use a graphing utility to graph the data from the table and the model in the same viewing window. How well does the model fit the data? Explain. (b) Determine the life expectancy in 1990 both graphically and algebraically. (c) Use the graph to determine the year when life expectancy was approximately 70.1. Verify your answer algebraically. (d) Find the y-intercept of the graph of the model. What does it represent in the context of the problem? (e) Do you think this model can be used to predict the life expectancy of a child 50 years from now? Explain.

• I think the model needs some editing. Is there a square missing? – Patricio Jan 12 at 9:31
• It seems that there is a typo in $0.97t/ 1 + 0.01t$. Are parentheses missing? Or is it 1/t instead of t/1 ? – Bertrand Jan 12 at 9:31
• I have checked and added the parentheses. – user633979 Jan 12 at 11:20
• No. I looked at it. This is the model – user633979 Jan 12 at 11:20