Step-by-step explanation:
We can model the annual consumption of iron by the equation
c = 900 million tons x , where
n is the number of years after 1993 and
c is the consumption for that year.
An estimate for the total consumption of iron can now be obtained by integrating this equation with respect to a dummy variable, x from 0 to n.
This equation simplifies to
C = 900 million tons x (1.025^n - 1) / ln(1.025), where
x is a dummy variable and
C is the total consumption of iron n years after 1993.
Let R be the amount of iron remaining at n years after 1993, so
R = 480 billion tons - C
R = 480 billion tons - 900 million tons x (1.025^n - 1) / ln(1.025)
We need to find the value of n when R is 0, so
0 = 480 billion tons - 900 million tons x (1.025^n - 1) / ln(1.025)
Simplify this equation to obtain
n = 107.4
So the iron will run out in the year 1993 + 107 = 2100
