SOLUTION: If you drive 2 h at 80 km/h, how fast must you drive during the next hour in order to have an average speed of 75 km/h?

Question 29329: If you drive 2 h at 80 km/h, how fast must you drive during the next hour in order to have an average speed of 75 km/h?
Found 2 solutions by longjonsilver, amalm06:
Answer by longjonsilver(2297) (Show Source): You can put this solution on YOUR website!
average speed = total distance/time taken

First, the initial part:
80 = distance/2
--> distance = 160km.

So, for average speed of 75, we have travelled 160+x, where x is the distance we are asked for. Total time is 3 hours. So,

(160+x)/3 = 75
160+x = 225
x = 65km.

jon.

Answer by amalm06(224) (Show Source): You can put this solution on YOUR website!
The total time taken for the trip is 3 hr and the total average speed is 75 km/h.

For this problem, average speed = average velocity = Δx/Δt

Therefore, Δx=(75 km/h)(3 hr) = 225 km

So the displacement for the remaining 1 hr is 225-(2)(80)= 65 km

Thus, you must drive 65 km/hr (Answer)
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