Question 1118675:  Suppose the annual cost per active-duty armed service member in a certain country increased from $80,000 in 1995 to $90,000 in 2000. In 1990, there were 2 million armed service personnel and this number decreased to 1.5 million in 2000. Use linear models for annual cost and personnel to estimate, to the nearest $10 million, the rate of change of total military personnel costs in 1998.  
 Answer by josgarithmetic(39630)      (Show Source): 
You can  put this solution on YOUR website! You may want linear models.  
 
 
This is not a complete solution, but just a way to start analyzing the description.  You want some data points.
 
 
Year  Set to time 0=1990    Price Per Person/Service Member   POINTS (t,p)
1995          5                80000                        (5, 80000)
2000          10               90000                        (10, 90000)
 
 
Year         time 0=1990         Number of Service Members    POINTS (t, n)
1990            0                 2000000                    (0,2000000)
2000           10                 1500000                   (10,1500000)
 
 
 
You use each pair of points to get linear equations for each.  Next, COST would be price multiplied by number of members, or    .  Be careful to notice, the two first sets of data points are based on a different time point value; so you may need to compute the needed price  to use for getting cost or Number of Members equation.
 
 
The actual question is about year 1998, for when t=8. 
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