Dattaprabhakar G. answered 08/30/14
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Humairaa:
The change in enrollment from 1990 to 2003 for (2003-1990=) 13 years is 48673-36531 = 12142.
(a) The annual average change is 12142/13 = 934.
(b) Year 1994 is 4 years from 1990. So the estimated change in enrollment is 4(934) = 3736.
Year 1998 is 8 years from 1990. So the estimated change in enrollment is 8(934) = 7472.
Year 2002 is 12 years from 1990. So the estimated change in enrollment is 12(934) = 11208.
Dattaprabhakar (Dr. G.)
P.S. You have told me that the problem, being on linear equations, must be solved by "linear interpolation". A more interesting problem is to estimate the enrollment using "compounding". To explain, starting from 36531 in 1993, after the first year, the enrollment increases to 36531 (1 + r), in the second year it increases to [36351(1+r)](1+r) and so on.It reaches 48673 in 2003. How to find r is interesting.
But that is probably beyond your scope, at least as of now. If you would like to know, please post a comment.