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Physics
OpenStudy (anonymous):

a person takes a trip driving with a constant speed of 89.5 km/h except for a 22 min. rest stop. If the average speed is 77.8 km/h, how much time is spent on the trip and how far does the person travel

OpenStudy (anonymous):

\[v _{avg} = \Delta x/\Delta t\] the total time for the trip is the sum of the time for the stop (22 min) + the time for the travel at 89.5 km/h, or \[\Delta t = 22/60 h + t _{89.5}\] Since the average velocity including the stop is 77.8km/h, using teh formula for average velocity \[77.8km/h = \Delta x/\Delta t = \Delta x/[(22/60) h + t _{89.5}]\] rearranging \[77.8 km/h*[(22/60)h + t _{89.5}] = \Delta x\] We know the driver drove at 89.5 km/h for the entire distance (no distance covered while stopped), so \[\Delta x = 89.5 km/h * t _{89.5}\] set the two expressions for the distance equal to each other and solve for the time, then use that value to calculate the distance

OpenStudy (anonymous):

Just to check if I did it correctly, does that make 19 minutes spent on the trip and 28.5 km (1dp) traveled?

OpenStudy (matthewrlee):

If you know that much about his speed why didn't you just ask him what time he left and what time he arrived? The math is a lot easier.

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