SOLUTION: It takes Joe 12 hours to paint a fence, but Bob can do the job in 9 hours. How long does Joe work by himself before being joined by Sam if they finish the job working 3 hours toge
Algebra.Com
Question 376475: It takes Joe 12 hours to paint a fence, but Bob can do the job in 9 hours. How long does Joe work by himself before being joined by Sam if they finish the job working 3 hours together?
I've tried setting up a system of equations, but am not having much luck. I think that the first equation is x/12 + y/9 = 1, with x being the number of hours Joe works and y the number of hours Bob works, but I can't figure out the second equation.
Found 2 solutions by nerdybill, ankor@dixie-net.com:
Answer by nerdybill(7384) (Show Source): You can put this solution on YOUR website!
It takes Joe 12 hours to paint a fence, but Bob can do the job in 9 hours. How long does Joe work by himself before being joined by Sam if they finish the job working 3 hours together?
Let x = number of hours Joe works by himself
then
"portion of work by Joe" + "work together" = "total job"
x/12 + 3(1/12 + 1/9) = 1
x/12 + (1/4 + 1/3) = 1
multiplying both sides by 12:
x + (3 + 4) = 12
x + 7 = 12
x = 5 hours
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
It takes Joe 12 hours to paint a fence, but Bob can do the job in 9 hours.
How long does Joe work by himself before being joined by Sam if they finish the job working 3 hours together?
:
We can do it with one equation, but I'm going to ignore Sam's contribution here
:
Let t = time Joe worked by himself
and
Bob works 3 hrs
and
(t+3) = total time Joe worked
:
Let the completed job = 1
:
+ = 1
Multiply by 36, results:
3(t+3) + 4(3) = 36
3t + 9 + 12 = 36
3t + 21 = 36
3t = 36 - 21
3t = 15
t =
t = 5 hrs Joe works by himself
;
:
Let's see if that is true (Joe works 8 hrs total),
8/12 + 1/3 = 1
RELATED QUESTIONS
Bob can paint a small house in 8 hours. Joe could paint the same size house in 10 hours.... (answered by hamsanash1981@gmail.com)
Kiyoshi can paint a certain fence in 3 hours by himself. If Red helps, the job takes... (answered by josgarithmetic)
joe can paint the barn in 11 hours by himself. Steve has never timed himself painting a... (answered by TimothyLamb)
A man can paint a room by himself in 8 hours and it takes his son 12 hours to do the same (answered by Earlsdon)
I have no idea how to go about this problem...or where to start. Help me please :(... (answered by rothauserc)
Sarah can build a fence in 9 hours. Joe can do the same in 6 hours. How long would it... (answered by richwmiller)
please help me with this problem ): I have no idea where to begin and how to solve this.... (answered by josgarithmetic,josmiceli)
Bob and Sarah need to paint a fence. Bob can paint a fence in 4 hours and Sarah can paint (answered by josgarithmetic,addingup,greenestamps)
Sarah can paint a fence in 4 hours. Her father Joe can paint it in 2 hours. If they work... (answered by ptaylor)