SOLUTION: I have a word problem that my professor wants me to use the straight line formula to do. I just can not figure out how to put the numbers in the right spot or what numbers to use!

Question 190549: I have a word problem that my professor wants me to use the straight line formula to do. I just can not figure out how to put the numbers in the right spot or what numbers to use!
The problem is Sales, given in thousands, for a particular compan in 1990 were at 140.5 and in 2000 at 180.5. Estimate the sales for theyears 1997 and 2003. Let x=0 correspond to 1990.
Answer by jojo14344(1513) (Show Source): You can put this solution on YOUR website!

Remember Problem # 189853? It is the same as this one right?

You were just looking a straight Line formula, Ax + By + C =0 and we we'll get there. The double interpolation we did is also one way of doing it.

Let x = Year and y = Sales:

If x = 0 for year 1990, then y = 140.5. This makes our Line Eq'n,---> x + y =140.5.

If x = 10 for year 2000, then y = 180.5. This makes our Line Eqn, ---> -4x + y =140.5 . Why?

Let's substitute x=10:

, correct.

Therefore, to find for Sales for the year 1997:

We use x=7 for year 1997:

, Sales for 1997

To find Sales for 2003, we use x=13:

y=140.5+52=192.50, Sales for 2003

See Problem 189853 again, the values are the same. There is a misprint but it was adjusted.

Your working Line Eqn, -4x + y =140.5 ( Answer )

Thank you,
Jojo
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