SOLUTION: Janet can wax her car in 8 hours. When she works together with Darlene, they can wax the car in 30 minutes. How long would it take Darlene, working by herself, to wax the car? I

Algebra ->  Matrices-and-determiminant -> SOLUTION: Janet can wax her car in 8 hours. When she works together with Darlene, they can wax the car in 30 minutes. How long would it take Darlene, working by herself, to wax the car? I      Log On


   



Question 111585: Janet can wax her car in 8 hours. When she works together with Darlene, they can wax the car in 30 minutes. How long would it take Darlene, working by herself, to wax the car?
Is it the same as this: If J=8 and D+J= 1/2 D is equal to what? I know the answer 8/15 hours i dont know how it is got
I dont know what topic is it?
Thank You very much

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
(janet's rate) + (Darlene's rate = (1 car / 1/2 hour)
(1 car / 8 hrs) + (1 car / D hours) = (2 cars / 1 hour)
1%2F8+%2B+1%2FD++=+2
multiply both sides by 8D
D+%2B+8+=+16D
15D+=+8
D+=+8%2F15 hr
or
D+=+32%2F60 hr
So, Darlene can wax the car in 32 min by herself