SOLUTION: This one is a application problem. I am unsure what formula to use to solve. It reads: A carpenter purchased 60ft of redwood and 80ft of pine for a total cost of $286. A

Algebra ->  Expressions-with-variables -> SOLUTION: This one is a application problem. I am unsure what formula to use to solve. It reads: A carpenter purchased 60ft of redwood and 80ft of pine for a total cost of $286. A       Log On


   



Question 263148: This one is a application problem. I am unsure what formula to use to solve. It reads:
A carpenter purchased 60ft of redwood and 80ft of pine for a total cost of $286. A second purchase, at the same price, included 100ft of redwood and 60ft of pine for a total cost of $396. Find the cost per foot of redwood and of pine.

Answer by drk(1908) About Me  (Show Source):
You can put this solution on YOUR website!
This requires a system of equations as follows
(i) 60r+%2B+80p+=+286
(ii) 100r+%2B+60p+=+396
step 1 - divide (i) by 2, and divide (ii) by 4 to get
(iii) 30r+%2B+40p+=+143
(iv) 25r+%2B+15p+=+99
multiply (iii) by 3 and multiply (iv) by -8 to get
(v) 90r+%2B+120p+=+429
(vi) -200r+-+120p+=+-792
add (v) and (vi) to get
(vii) -110r+=+-363
solve for r as
r+=+3.30
and then we find p as
p+=+1.10