The average life expectancy for American men born in 1900 was 55 years. Life expectancy has increased by about .2 year for each birth year after 1900.
If this trend continues, for which birth year will the average life expectancy be 85 years?
how do u write and equation for to solve this?
Let life expenctancy = L . Let y be the number of years after 1900.
L = 55 + 0.2 y = 85
Solve that equation for y
0.2 y = 30
y = 150
That would make the birth year 2050 for a life expectancy of 85.
To write an equation for solving this problem, we can assume that the birth year is represented by the variable "x" and the average life expectancy is represented by the variable "y".
According to the information given, the average life expectancy for men born in 1900 was 55 years, and it has increased by 0.2 years for each birth year after 1900.
Based on this, we can write the equation as:
y = 55 + 0.2(x - 1900)
In this equation, "y" represents the average life expectancy and "x" represents the birth year.
Now, to find the birth year when the average life expectancy is 85 years, we can plug in "85" for "y" in the equation and solve for "x":
85 = 55 + 0.2(x - 1900)
Now, let's solve for "x":
85 - 55 = 0.2(x - 1900)
30 = 0.2(x - 1900)
Dividing both sides by 0.2:
150 = x - 1900
Adding 1900 to both sides:
2050 = x
Therefore, if the trend of increasing life expectancy continues, the birth year when the average life expectancy will be 85 years is 2050.