SOLUTION: In 1990, 528,000 people worked in the air transportation industry. In 2006, the number was 484,000. a) Find a linear equation giving the number of employees in the air transporta

Algebra ->  Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: In 1990, 528,000 people worked in the air transportation industry. In 2006, the number was 484,000. a) Find a linear equation giving the number of employees in the air transporta      Log On


   



Question 1095208: In 1990, 528,000 people worked in the air transportation industry. In 2006, the number was 484,000.
a) Find a linear equation giving the number of employees in the air transportation industry in terms of x, the number of years since 1990.
b) Assuming the equation remains valid in the future, in what year will there be 430,000 employees of the air transportation industry?
PLEASE INCLUDE VERY DETAILED SOLUTIONS, since I have had trouble with my calculations and need to see what I'm doing wrong.
Thank you very much,
computerlove27

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Plot number of employees, +y+, on vertical axis
Plot time, +t+, in years on the horizontal axis
You are given 2 points on a straight line
( 0, 528 )
( 16, 484 )
The y-axis is thousands of employees
---------------------------------------
(a)
Use general point-slope formula
+%28+y+-+484+%29+%2F+%28+x+-+16+%29+=+%28+528+-+484+%29+%2F+%28+0+-+16+%29+
+%28+y+-+484+%29+%2F+%28+x+-+16+%29+=+44+%2F+%28-16%29+
+%28+y+-+484+%29+%2F+%28+x+-+16+%29+=+11%2F%28-4%29+
Multiply both sides by +%28-4%29%2A%28+x+-+16+%29+
+%28-4%29%2A%28+y+-+484+%29+=+11%2A%28+x+-+16+%29+
+-4y+%2B+1936+=+11x+-+176+
+4y+=+-11x+%2B+2112+
+y+=+%28-11%2F4%29%2Ax+%2B+528+
( note that number of employees is in thousands )
----------------------------------------------
(b)
+y+=+430+
+430+=+%28-11%2F4%29%2Ax+%2B+528+
+%2811%2F4%29%2Ax+=+98+
+x+=+%284%2F11%29%2A98+
+x+=+35.6364+
1990 + 35 = 2025
During 2025, there is 430,000 employees
----------------------------------------
Check the equation:
+y+=+%28-11%2F4%29%2Ax+%2B+528+
( 16, 484 )
+484+=+%28-11%2F4%29%2A16+%2B+528+
+484+=+-44+%2B+528+
+484+=+484+
OK
( 35.6364, 430 )
+430+=+%28-11%2F4%29%2A35.6364+%2B+528+
+430+=+-98.0001+%2B+528+
+430+=+430+ ( very close )