SOLUTION: david travel 200 km at certain speed if he had driven 10km faster the trip would have taken 1 hour less determine Davids speed

Question 756181: david travel 200 km at certain speed if he had driven 10km faster the trip would have taken 1 hour less determine Davids speed
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
david travel 200 km at certain speed if he had driven 10km faster the trip would have taken 1 hour less determine Davids speed
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d = r*t
t = d/r
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t = 200/r
t-1 = 200/(r+10)
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Sub for t in the 2nd eqn
200/r - 1 = 200/(r+10)
(200-r)/r = 200/(r+10)
-200r = r^2 - 190r - 2000
r^2 + 10r -2000 = 0
(r+50)*(r-40) = 0
r = 40 km/hr

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