Answer:
In 2011 the world's population will be 7 billions
Step-by-step explanation:
Lets choose January 1, 1993 as 0 time, so January 1, 1998 is time 5, because is 5 year after.
As the population grows at a ate proportional to the population at that time, we can determinate the linear relationship between the time and the world's population.
We have two point:
January 1, 1993 (x1=0) ⇒ world's population was 5.51 billion (y1= 5.51)
January 1, 1998 (x2=5) ⇒ world's population was 5.88 billion (y2= 5.88)
The linear relationship between this two variables can be represent by the equation:
y=a*x+b (linear function)
a ⇒ slope
b ⇒ intercept with y-axes
a==
b=y-a*x
Using (x1,y1)
b=5.51-0.074*0=5.51
y=0.074*x+5.51
Now we can estimate how many years from 1991 the population will be 7 billion
y3=7
x3= ?
(y3-5.51)/0.074= x3
(7-5.51)/0.074=x3
20.135=x3
The result is not an exact value, but this decimal value will represent a few extra days after January 1, 2011 (20 years after January 1, 1991), but as the question as for a calendar year and not and exact day we will just work with the 20 years
We can say that in 2011 the world's population will be 7 billions