Posted by Andrea on .
A car manufacturing company (the Company) can produce a car for $3000.00 and a truck for $5000.00. Suppose "C" cars and "T" trucks are sold to the dealer at markups, respectively, of 20 and 30 percent. If the Company made a profit of $27 million on sales of $137 million in one particular year, how many cars and trucks were sold by the company in that year?
I have to get 2 equations from this and use the substitution or elimination method

PreCalculus 
drwls,
The first equation would be
3000 C + 5000 T = 137,000,000 (total sales)
The second equation would be
3000*.20*C + 5000*.30*T = 27,000,000 (profit)
This can be rewritten
600 C + 1500 T = 27,000,000
Now solve those two equations for C and T, the number of cars and trucks sold, using either method. 
PreCalculus 
Andrea,
I tried it this way and my answer for

PreCalculus 
Andrea,
I tried to solve it using those equations but my answer for T is a negative number which I know it can't be

PreCalculus 
drwls,
I get the same result as you, and checked my work. I have no explanation

PreCalculus 
Brandon,
Sometimes one winds up with an "erroneous" solution.