SOLUTION: Jeff and kirk can build a 75 ft retaining wall together in 7 hours because Jeff has more experience he can build alone in two hours quicker than kirk. how long can it take kirk to
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Question 834235: Jeff and kirk can build a 75 ft retaining wall together in 7 hours because Jeff has more experience he can build alone in two hours quicker than kirk. how long can it take kirk to build the wall alone? round to the nearest minute.
thank you I am so stuck on this question I don't know what to do Answer by ankor@dixie-net.com(22740) (Show Source):
You can put this solution on YOUR website! Jeff and kirk can build a 75 ft retaining wall together in 7 hours
because Jeff has more experience he can build it alone in two hours quicker than kirk.
how long can it take kirk to build the wall alone? round to the nearest minute.
:
Let t = time required by Jeff to build the wall
then
(t+2) = time required by Kirk
:
Let the completed job = 1 (a completed wall)
:
Each will do a fraction of the wall, the two fractions add up to 1 + = 1
multiply by t(t+2), to clear the denominators, resulting in:
7(t+2) + 7t = t(t+2)
7t + 14 + 7t = t^2 + 2t
14t + 14 = t^2 + 2t
A quadratic equation
0 = t^2 + 2t - 14t - 14
t^2 - 12t - 14 = 0
Using the quadratic formula, the reasonable approx answer
t = 13.071 hrs
Kirk takes 2 hrs longer, therefore
15.071 hrs for Kirk
Find the hrs and minutes
15 + ..071(60) = 15 hrs 4 minutes
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