Question

1 point) According to one mathematical model, the average life expenctancy for American men born in 1900 was 55 years. Life expectancy has increased by about 0.2 year for each birth year after 1900. If this trend continues, for which birth year will the average life expentancy be 73 years?
a) Write an equation to model the problem. Let t represent the number of years after 1900. For example, t = 12 would represent the year 1912.

b) Solve the equation, then answer the question given above. (Note: You are asked for a year, not a value for t.)

Answer 1

  a)

Let t represents number of years after 1900

so that means for 1900, value of t is 0

We are given point as (0,55)

and it says that life expectancy increases by 0.2

so that means slope,m=0.2

equation of line is y=mt +b

or y=0.2t +b

now we use point (0,55)

55 =0.2(0) +b

55 =0+b

55= b

so b=55

plug it back into the equation,we get

y=0.2t +55

b)

We are given y=73

so we plug it into the equation we got in part a and solve for t

y=0.2t +55

73 =0.2t +55

73-55 =0.2t

18 =0.2t

18/0.2 =t

90 =t

so t=90

This means the birth year =1900+t =1900+90 =1990