Question 33420
YEAR _t _N
1992 _0 4032
2002 10 3682


First thing is to assume a linear relationship rather than some sort of curve.


This will be of the form y=mx+c or with our variables N=mt+c. We need to find the gradient m and the y-intercept, c.


We can find c straightaway: when t=0, N=4032, so from N=mt+c we get
4032 = m(0) + c
--> c = 4032


so we have N=mt+4032


Now for the gradient:
gradient, m = (change in y)/(change in x)
m = (3682-4032)/(10-0)
m = -350/10
m = -35


--> N = -35t+4032


In 2007, t = 15, so N = -35(15)+4032
N = -525+4032
N = 3507 stores


No stores is when N=0, so 0 = -35t+4032
35t = 4032
t = 115.2
so after 116 years, so in year 2108, if the number of closures followed the same rate.


jon.