SOLUTION: Can you help me solve this problem: A repairman purchased some washing machine motors for a total of $224. When the unit cost decreased by $4, he was able to buy one extra motor fo

Algebra ->  Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: Can you help me solve this problem: A repairman purchased some washing machine motors for a total of $224. When the unit cost decreased by $4, he was able to buy one extra motor fo      Log On


   

Question 163453: Can you help me solve this problem: A repairman purchased some washing machine motors for a total of $224. When the unit cost decreased by $4, he was able to buy one extra motor for the same total price. How many motors did he buy originally?
Answer by edjones(8007) About Me  (Show Source):
You can put this solution on YOUR website!
Let n=number of motors & u=unit cost
A) n*u=224
B) (n+1)*(u-4)=224
.
A) u=224/n
B)
(n+1)*(224/n -4)=224
(n+1)((224-4n)/n)=224 LCD of 224/n -4
(n+1)(224-4n)=224n multiply each side by n to eliminate the fraction.
-4n^2+220n+224=224n
n^2-55n-56=-56n divide each side by -4
n^2+n-56=0
(n+8)(n-7)=0
n=7 motors at $32
8 motors at $28
.
Ed